This is a great quote that Zillow COO Spencer Rascoff heard at the conference he is currently at (and tweeted a few minutes ago):

You need a person in your life who is 100% honest with you and can tell you you’re an idiot.

I 100% agree. Luckily, I have several close friends who can and do tell me when I’m being an idiot. If you don’t have people like that in your life, find a few of them. Otherwise, you’ll keep on doing idiotic things without even knowing it.