As a former douchebag, the best way to realize what your doing is by:

Looking around you for people who do similar things and see how stupid they sound. This is for real douchebaggery, not stupid shit like pings which upset people. I mean really trying to make someone feel bad, when you see someone else doing this to another person it puts you in perspective of how the things you say are affecting others. If you're not whatsoever affected by that, you are probably letting something stress you out to the point of blocking emotions and releasing them on others.