Ask HN: How to determine when to give up?

I've gotten some good advice about quitting from the book "The Dip" by writer Seth Godin. #nopromo http://hubpages.com/business/theDipBook

This is _the_ resource on giving up - I just re-read it like a month ago because I had some doubt about giving up on my current project or keeping on.

(I keep on)

It is basically impossible. The best I can add is give up when you can live with yourself for giving up. If you can in hindsight say you gave your all and it didn't work then that is the time to give up.

When the downside risk will become unacceptable if you continue.