it is allah who created you weak then after weakness gave you strength then after strength gave you weakness and old age he creates whatever he wills and only he is the all knowing the able.
الله الذي خلقكم من ضعف ثم جعل من بعد ضعف قوة ثم جعل من بعد قوة ضعفا وشيبة يخلق ما يشاء وهو العليم القدير