Isn’t the best version of yourself just you? I mean, the best you can’t be any better than you already are. You are you, so to say. There is no “best” you, or “worst” you. There’s you and your ego, maybe, but that’s about it.
Self-improvement is bullshit. If you let go of everything, let go of your ego, you are as much you as you can be. I suppose you could say that is self-improvement, but I’d say it’s more of self-abolishment. Fuck all the methods of becoming as good as you can be. Let go of the methods, of your thoughts, and you become the best you. Simple as that. Just let go.