To quote a friend of mine, 'it's pointless to doubt yourself. It only reduces what you can do.'

My meta-suggestion is to find things that you enjoy or care about (not the same thing) enough to put effort into handling them them better. Giving advice in general doesn't seem to fall into that category - I don't remember seeing you do it regularly, which is the only measure I really have access to - but you seemed pretty engaged in this case, so there may be an aspect of this situation that you care about more than you would care about a run-of-the-mill situation. If there is, and if you can figure out what it is, you can use that information to find more things of that type, which is likely to be useful - you run into that 'having something to protect' effect.