Praise be to Allah, and may peace and blessings be upon the Messenger of Allah.
Belief in divine decree is one of the pillars of faith. It includes believing that Allah تعالى knew the decrees of all created beings, wrote them, willed them to occur, and created them. Allah تعالى says: “Indeed, We have created everything according to a decree.” [Al-Qamar: 49] And He سبحانه says: “And you do not will unless Allah, Lord of the worlds, wills.” [At-Takwir: 29]
Nevertheless, the servant has will, choice, and ability, and he acts according to his own will. Therefore, he is rewarded or punished. However, his will is subordinate to the will of Allah تعالى, and nothing falls outside His decree.
Accordingly, if by saying “I create my own destiny” a person means that he can escape Allah’s decree, or change what Allah has decreed independently of Him, or that he does not believe in divine decree, then this is falsehood and misguidance, because it contradicts the fundamental principle of belief in divine decree.
But if the speaker means that he chooses his actions, strives and makes an effort, does not feel that he is forced to perform his actions, and does not use divine decree as an excuse for abandoning action, then this meaning is correct in principle. However, the expression itself is not appropriate, because it gives the impression that a person creates his destiny independently of Allah’s decree.
It is better to say: “I choose, strive, and take the appropriate means, and all of that is within Allah’s decree and will,” while believing that whatever Allah wills happens, and whatever He does not will does not happen.
In summary: One should not use the expression “I create my own destiny” without qualification, because it is an ambiguous statement. If it means independence from Allah’s decree, then it is false. If it means affirming the servant’s will, choice, and taking of means, then the meaning is correct, but it should be expressed in clearer and safer words.
And Allah knows best.