When you're not humble enough, bad things happen. When you're too humble, good things that would have happened don't happen. That makes it harder to regret being too humble, because you usually don't know about the things that could have happened.
I always struggle to figure out when I'm crossing the line from being humble to self-deprecating (the latter not always being a good thing and something I've regretted on occasion).
One single job interview where they ended up hiring the guy with nearly identical qualifications. The guy leading the interview later told me on the phone "it was almost 50/50, but we had to pick only one of you", and the reason was that the other person appeared slightly more confident in his abilities using a particular framework. If I'd have been a bit more self-promoting, that could've been me. Lesson learned, of course.
Of course there's a difference between confidence and being brash.
