I've been playing Go with Guillaume; it's a lot of fun, but occassionally I get boneheaded and just don't know when to resign. It's bad courtesy, and I should be better about it. There's a difference between optimism and denial, and I resolve to tell the difference better next time.
There's also a point when one is programming something difficult; sometimes I feel like I should resign and step back and see that my approach is altogether wrong. But there's the mythology of the heroic programmer --- that one last bug fix, and maybe-if-I-fiddle-with-this-it-will-work syndrome --- that I'm still enamored with.
This fault runs deep in me, and I will need to retrain myself to be less silly.