They always said "just be yourself", which is helpful, but there's a problem. Maybe I'm over analyzing this, but if I'm always myself, how could I ever be a better man? What I mean is, "myself" is flawed because I'm human. Humans are selfish, so I'm selfish. I've been known to be defensive. Sometimes, I won't stick to my promises, even those promises I made on myself. I'm too opinionated and give advice when it's not requested (case in point). Then there's my whining and worrying about petty problems. In other words, being myself only works when it's reflecting the better sides of my nature.
Of course, I understand the sentiment of "be yourself", but for the sake of being contrarian (another flaw), here's an idea. "Don't be yourself, be the version of the person you want to be." Sure it's long winded, but works. Just do things according to your better version. Imagine your life as a movie, where you're the hero instead of the villain.
When you feel the urge to say something mean behind someone's back, consider this character. Think about how he/she would act. Picture them being nice, even when they have every reason to be rude. Consider how this version of you, would live your life. I think this works for one simple reason. You're getting outside of your head, detaching from a self centered point of view, and thinking clearly about who you want to be.
This not only improves your well-being, but the well-being of those around you. Because we could all use better versions of ourselves. We have enough critics, enough anger and enough animosity. We have too many villains. So don't be yourself, be the version of the person you want to be.
Or don't. I'm trying to stop telling people what to do. So do what you want.