I shrug it off and either take the criticism and revise, or move on, or both. It's also helpful when I always keep 2 or 3 ideas rolling at the same time, so if one doesn't go anywhere I've got other things to immediately focus on.

Just keep going... I've realized if I stop creating, I die inside lol but seriously... did no one like it? Or just the people you thought would/wanted to like it? I'd find out why and if it's a valid point, then try to work it out differently in my next work. If it's not valid criticism then just ignore and keep creating until you find your audience. Is what I have done and do.