Today is the first day. Not of the rest of your life, because that would presuppose you had been living before now. Or that you had a life. Or that there was a you. All of which are highly controversial theorems.
"I could be bounded in a nutshell and count myself king of infinite space," said Hamlet. And if you were, would you be just another nut in its shell? Or would you be finally privy to the clue that solves the whole conundrum? Ask yourself that, today, on the first day.