How do you know when it's done?

How do you know when you've done enough to your art project, and it's time to call it quits? How do you know when you've added enough color, embellishments, texture, when enough is enough?I started putting together a collage in an altered book. I put down some vintage paper scraps, washi tape and slickers, and covered it over with gel paste. After that I used some distress inks to put some color on it and used brown paint around the outside for some contrast. I was ready to stop there.The rubber stamping was on the scraps that I tore up and glued on to the page. The letters were just random alphabet stickers I wanted to use up.The more I looked at it, the more I thought that it was missing something. I was thinking that it all looked a little too monochrome and needed something to stand out. I decided on using a stencil in bold black ink.I liked it but then thought I went a little too bold on the left. The black was too dark. And the one on the right, though lighter, just seemed to be floating on the page; it wasn't grounded. Not good.So then I thought, what else could I add? How about lace? It definitely adds something.The stencil on the right doesn't look like it's floating anymore. And the lace balances the starkness of the stencil on the left.Okay, now I think it's done.