Have you ever read a book and realized that you have no idea what the last couple of pages said, so you have to go back and reread them? Life strikes me like that sometimes. I can reach the end of the week and have no idea where the days went. What did I do? It's sort of like exiting an epileptic fugue. Unlike reading a book, though, I can’t go back. There are no do overs, and lost days remain lost.
Thank goodness, it's never too late to start. Look at writers who have done marvelous work later in life. Frank McCourt published Angela's Ashes, his first book, when he was sixty-six. Norman Maclean's first collection, A River Runs Through It and Other Stories wasn't published until he was in his seventies. So it is possible to delay a writing career and still do well, but we don’t know that we have that luxury. Look at the writers who were cut off (or cut themselves off) too soon: Stephen Crane (29), Emily Bronte (30), John Kennedy Toole (31), Sylvia Plath (30), John Keats (25), Edgar Allan Poe (40), etc.
Life is short. The days rush by. If you really want to write, does it make sense to say, "I'll get started next year"? or "I have too many responsibilities now. I'll write when I get past this rough patch"? or, even worse, "What happened to the time?"