Just because you believe something, it doesn’t make it the truth.
You can believe that you have enough time to accomplish anything, but the reality could be that you barely have enough time to do one thing well.
And if that’s the case, pursuing a hundred things will likely lead you to a hundred dead ends.
Recognizing the reality and admitting it is the first step you need to take to make the most of what you really got.
If you have enough time for only one thing, decide what that is and pursue it rigorously.