There’s a lovely Hadith Qudsi, (Sacred Hadith) sub-category of “Hadith” which are sayings of Muhammad, that we Muslims regard them as words of God, that says:
What is yours you shall have despite your weaknesses. What is not yours you won’t have despite your might.
It emphasizes that fact that we human beings sometimes worry too much about what might happen, what we may or may not achieve, without acknowledging that everything is moving upon God’s will.
This doesn’t mean that we are supposed to lay back, relax and do nothing since everything is predestined, that would be considered apathy and neglectfulness. But we are rather supposed to chase our goals and dreams with this spiritual assurance, that whatever we encounter is upon God’s plan and not ours, and therefore for our best.