It's from this show I used to watch called Everwood. I don't suppose many people know wat it is, but I liked it growing up... It'll always mean something to me haha, it's actually wat got me into reading mangas (even tho it hardily had a place in the show) but there was a guy in there... Harper, who always started each episode with a meaningful and philosophical message to convey. And this is from the last page of the book he wrote in the show.

The Last Page of Harper's book:

I've made my mistakes, and now I have my regret to keep me company.

Voices and books for Friends.

I've walked away from my life's work and she doesn't even know it.

I know I should move on, let it end there, with loss excepted. I know I should go, something keeps me still.

There isn't so much a cure for regret as a remedy, you can sit and mourn all you did wrong, writhe in the empty phantasy of how you do it better if only you could go back.

Or you can do it better now.