BE yourself. Just, you know, be yourself. Your TRUE self. The self you know yourself to be, because, listen, that's enough. You're great, if only you realized that just being who you are is totally and completely enough and wonderful. People just need to be themselves instead of trying to be, you know, "better" than themselves. That's just gonna make us sad and we don't like sadness! Sadness is depressing and unattractive. And if everyone was just themselves then no one would ever be sad. They'd be themselves. We'd all be ourselves, basking in our own selfiness, and A-OK! And you are absolutely not allowed to not like yourself. Insecurity is so '90s, and it's not OK anymore. In fact, if you don't like yourself, you know what, keep it to yourself because we ourselves just don't need to hear about you and your fucked-up perspective on yourself. That may sounds selfish, self-serving, but whatever, it's the gestalt.
You know what? I say, be better than yourself, yourself is a start, but I mean come on, you know and I know that you need a lot of work. How's that ever gonna happen if you just go around being yourself and being OK with yourself?
Also, what the hell is a self? That guy from the Verve was a million different people and he was kinda shallow (just look at that picture!). You? Me? We're at best an arena of semi-consistent traits, some good, some bad, that have some statistical probability of manifesting themselves in certain situations, but certainly don't amount to some unitary platonic self. We're quantum, a range of stuff, and none of us knows what the hell is going on, not really.
Just remember, the next time someone tells you to "just be yourself" they're not making any sense at all.