For his sake, there are angels following one another, before him and behind him, who guard him by Allah's commandment, surely Allah doesn't change the condition of the people until they change their own condition; and when Allah intends evil to a people, there is no averting it, and besides him they have no protector.
—[Ar-R'ad verse 11]
This verse in the holy Qur'an states that Allah is the protector of human beings and he has commanded angels to protect us. No one else is protecting human beings. Even if someone says that I will protect you, I will defend you then he can only do so by the consent of Allah (صلى الله عليه وآله وسلم). So, no one has any authority to protect a person and the command belongs only to Allah.
But it doesn't mean that everything what you do, Allah will protect you. It doesn't mean that a human being cannot do anything about his destiny and in his defence. Here this topic becomes complex.
If Allah is protecting us through angels and he is our lord, the greatest, the mighty; that doesn't mean Allah is handling all our affairs and we are free to sleep in a corner, and all will be in place automatically by the command of Allah. Allah has given us two hands, two legs, a brain, a face and (the most important) a self (soul) that he has perfected for us.
"Wa Nafsinw Wamaa Sawwahaa"
"And the soul and him who made it perfect" [Surah Ash Shams 91:7]
Now, we have to make use of all this. Isn't it enough to live a good life or to identify the Truth? Isn't it enough to forbid evil and practice good?
True that Allah is our protector and Allah is our guide and no one is guided except the one guided by Allah. True that, all are poor and paupers except the one who is provided by Allah. As it is said by Maula Ali (عليه السلام) in his Munajaat:
"Mawlaya Ya Mawlaya, Antal ghaniyu wa Anal Faqeer wa hal yarhamul faqeera illal ghani"
"My Lord, O my Lord, you are the rich and I am a pauper and who is merciful to a pauper except the rich."
So, does that mean we should stop planning, stop working and just ask Allah and move ahead. Does that mean we should accept what our vibes say and make decisions instead of making decisions through logic and reason and far-sightedness? No. Why would Allah grant us with the gift of different elements of the body if we have to close them off and just go with the flow.
Imam Ali (عليه السلام) says in Nahj ul Balagha:
"All the illnesses and defects are in the soul itself and the cure to all our problems is also present in our 'self' only."
Also, "The one who identifies his self (soul) has identified his lord." — Imam Ali (عليه السلام)
So, all this talk that 'All is written and we can't do anything and that which has to happen will happen etc' are not completely true. To say rightly, these are fake spiritual talks. As, Imam Ali (عليه السلام) clearly says that All is clearly within us. What are we searching for? What else do we need?
Now, arises the question of fate. If all what I said is true then what about fate? I am not a denier of fate. I agree that it exists. Existence of fate cannot be denied but it is not the ultimate reality. Our fate is in our own hands.
We can change it through our actions, supplications, good and bad deeds. When Allah sees what we are doing and how we are living and behaving, Allah changes it accordingly. My statement is an opinion but it can be easily verified through Qur'an, Hadith and also the views of Arifeen.
Don't sit idle and don't think you are divine and you will hear a voice from unseen. Act according to your state and stay patient for the rewards. If you fail try again instead of saying that, "It is my fate. what can I do?" How do you know it is your fate!
Imam Ali (عليه السلام) says, "A wise man is the one who thinks before he speaks whereas a fool is the one who speaks before he thinks." So, this is simply foolish to say that you failed or lost because Allah has destined that for you. You get what you sow. A person's actions, his quest for something is itself a tool to change his fate and destiny. And that is what the verse I stated above says. Definitely, Allah is our protector but: '...Allah doesn't change the condition of the people until they change their own condition....' [Part of the verse stated in the start]. This clearly means that Allah is protecting us but Allah has made us incharge of our own affairs and it's only we who can change our own condition. Accepting the destiny is wise if we know our destiny. But who knows his destiny except Allah, The Great, The All Knowing.
Instead of getting into this querrel of fate, human being should try to focus upon action. As Ayatullah Taqi Behjat (May Allah be pleased with him) says: "May God give us the tawfeeq to perform our duties, that we don't be deprived of [performing] actions, not from within ourselves, neither from outside of us." Performing actions doesn't mean denying fate or denying the authority of Allah. Rather, it means accepting the blessings and opportunities provided by Allah, exploring them and exhausting them in the best way possible. We should understand that when we pray, Allah wants that we would ask him about something huge which a person is really deprived off and feels it as his necessity. Rather than asking that which Allah has already provided. Besides asking from Allah we should pray that "May Allah give us the tawfeeq to see what Allah has already blessed us with." We should explore within ourselves.
"You presume that you are a small entity, but within you presides an entire Universe."
The verse I started with is an excuse to explain this relationship between fate and action. Aim is not to discuss the correct interpretation of the verse itself but just a part of it. My aim is also not to do a detailed discussion on fate and action but rather to only address the confusion between the two things. Normally, we notice in our society that this discussion is quite prevalent. Like many big conflicts in the world, the conflict of fate and action also ends up into two extreme parties. One (which I might call a pretend-saint) that says Fate is everything and nothing is in our hands. Whereas other which denies every role of fate and destiny completely and declares actions to be the only basis of different events occurring in life. While both have their reasons, both are wrong. This conflict is important to be addressed because it has a psychological effect. Obviously, a person who thinks that all is written and he is powerless will do nothing. He will sit and keep on denying on the blessings Allah has bestowed him with. He will act like a hopeless lazy person who is deemed to deviate from his path. This notion even if small in quantity is an evil notion and will cause problems in ones life.
On the other side, the people who deny Fate and destiny. Such people are in true denial of god. This idea that only actions are the player behind what happens in life is also problematic because it cannot answer the many mysteries of life. Who can you blame for a natural disaster? The Japenese people, the Iranians; who are considered to be the most intelligent among the mankind live in those regions of the world where a lot of natural disasters occur. If we say that Japenese suffer because they are infidels then it would be the most lamest answer to the question. What about Iranians? So, actions matter but fate has it's own part. It is their to prove that Allah is the absolute and above everything. It doesn't mean that actions will not bear any fruit. Every action taken will have a reward or punishment but who knows when?
So, let us harmonize this. Let us end the blind beliefs occurring in our society due to the notion that 'Fate is everything and all depends on fate'. As is stated in Surah Al Asr:
"By the passage of time! Surely humanity is in grave loss, except those who have faith, do good, and urge each other to the truth, and urge each other to perseverance." 
So, it is certainly important to act without thinking about the fate. Removing all these blind beliefs about fate will lead us to passivity. Though, it seems small but in our traditionalist society, this idiocity is a huge problem. It has even entered the mentality of the educated and literate people because naturally it has nothing to do with education. It is because of overthinking and wrong mindsets and understandings about fate and destiny. It is because of ignorance and being illiterate is not a bad thing but being ignorant is equal to infidelity. To clarify, I am not calling anyone infidel but rather calling ignorance as infidelity.
Let us also tell the arrogant human beings that whatever they might do, the destiny finally belongs to Allah. As is said in the above stated verse, in the last: '...and when Allah intends evil to a people, there is no averting it, and besides him they have no protector.'
Fate is something that already exists like some fundamental basis of events, while action is something that we build upon our fate. If they are weak, they won't change our fate. If they are strong with a true devotion, they will change our destiny according to their nature. If it is an evil action, our destiny will become worse then what it was. If our action is good, our destiny will become better than what it was.
"So whoever does an atom’s weight of good will see it."
[Surah Zalzala 99:7]
"And whoever does an atom’s weight of evil will see it."
[Surah Zalzala 99:8]