You do not engage in any matter or recite any of the Qur'an or do any action without Our witnessing you while you are occupied with it. Not even the smallest speck eludes your Lord, either on Earth or in heaven. Nor is there anything smaller than that, or larger, which is not in a clear book. (Surah Yunus, 61)
As revealed in the Qur'an, Allah knows every situation of a human being is in, right down to the finest detail. Because it is Allah Who has created all the states and situations in which they find themselves. Allah creates every single detail, a thought passing through someone's mind, a sensation of pain occurring somewhere in the body, the book they are reading at that moment, which particular book it is, the page and even the individual word, and all these things are within His infinite knowledge. Allah creates any event that person experiences at that moment, right down to its finest detail, what is being said about them, the telephone that rings and the person on the other end of the line. Every one of these things will inevitably take place in the destiny ordained by Allah. Our responsibility is to be aware of this, submit to Allah with all our hearts and give profound and sincere thanks to Him.
The fact that Allah creates all things with a destiny is one of the greatest blessings. Destiny is a great source of ease and comfort. Someone who believes in destiny and knows that Allah has created everything in his life, everything he has and will encounter throughout that life, within that destiny will enjoy the comfort, security and inner peace stemming from that knowledge for the whole of his life. People who believe in destiny are at ease since they never worry about tomorrow. They never trouble themselves and fret about what tomorrow will bring. They know that Allah will create tomorrow in the most auspicious manner for them.
They are not worried about the future because they know that everything in the future is already ordained within the destiny of Allah, and that Allah prepares everything for them, their food, their clothes, their homes and their jobs. They still devote themselves to the natural causes behind these, but still realize that Allah will give these things to them if these causes exist in His destiny, and are therefore submitted to Him. People who believe in destiny are never saddened by their mistakes. Because they know that Allah has created those mistakes in the destiny He has appointed for them, and they reflect on the goodness and wisdom within them. They repent and strive not to make those same mistakes again. They know that Allah creates life with much wisdom and goodness in destiny to allow them to repent. Believers in destiny also know that the moment of their death is also destined, and that Allah will take back their souls at a time, in a place and in a manner of His choosing. They know that when the time Allah has ordained to take back their souls comes, nobody and nothing can protect them. They therefore put their trust in Allah. Since they believe and trust in Allah they hope for a delightful life in the Hereafter. They enjoy the ease of conscience that comes from living for Allah's approval and believing in His destiny. People who believe in destiny are always at peace because they never fear becoming the sufferers of injustice. They trust in Allah and know that Allah knows all and is infinitely just. They know that everything that happens to them, every response they give in the face of Allah and every word He hears are all ordained in destiny. They know that they give every response and speak their every word because Allah so wills. People who are aware of all this and who know that Allah has created everything to perfection within destiny are happy, resigned and at peace.