If one attempts being, one can only succeed or fail at doing. You do not have to do anything. You are not here to cure cancer or save the planet or write the great novel or even feed the hungry. You are here to be. You do not need a reason to live or a purpose to fulfill. You are not here to try or attempt any great work. There is no because. What you will do is feel and think, love and hate, laugh and cry, promise and regret, feel pride and shame, hope and despair, succeed and fail. And all of this will tempt you to kneel before the idol of CRITERIA that thrives on doings rather than beings.
If I had to put a phrase on this that suggested why you are here on earth, I can think of nothing more appropriate than “for the glory of God.” My atheist friends will of course object and say that “for the glory of God” means nothing more than “just because.” But Just Because is another name for God (Remember the divine name God revealed to Moses at the burning bush: https://en.wikipedia.org/wiki/I_Am_that_I_Am). And Grace is another name for being, which does not require any justification at all.