How do we reconcile our belief in divine decree (qadaa' and qadar) and that all our affairs are predetermined by God, with our freedom of choice? And what is the wisdom in contemplating the right choice if everything is already predetermined?

Allah Almighty created everything with a measure, and the actions of His servants are part of His creation, including their movements, thoughts, and choices. Evidence for this includes His Almighty saying: "Indeed, We created all things with a measure," and His saying: "While Allah created you and that which you do," and His saying: "And you do not will except that Allah wills." The servant is held accountable for what he does by choice, and he is forgiven for what he did unintentionally or under compulsion. He must exert his effort and strive to achieve his ambitions, knowing that everything is predestined, and he will only attain what Allah has decreed for him. The Prophet, peace and blessings be upon him, clarified that action does not contradict destiny, saying: "Work, for everyone is facilitated [to what he was created for]." Thus, the hadiths prohibit abandoning work and relying solely on destiny.