If this question comes from a place of hurt and sadness, because you've been bullied or made fun of, or hated for who you are with no other basis, then I say NEVER stop being yourself. You are you, wonderfully created and wonderfully made.
However, if this is coming from a place of conscious self reflection, and you want to "stop being yourself" in the sense that you want to improve yourself, you're angry at the person you've become based on your actions or behaviours as of late, then the first step is to admit that you are not proud of what you've done or how you've acted. Own up to it, accept it, then leave it behind you, because you are on a new path now. Next comes the desire, the TRUE desire, for your own sake and your own health, not to change, but to evolve and improve. With that, the possibilities are endless, and only you can find a strategy that works for you. For me, to become a more positive person, it was a lot of writing down positive things, buying things for myself that make me happy, redecorating, lighting a candle, etc. Joining facebook groups centered around positivity and the law of attraction. That's what worked for me and continues to work for me on my journey, however, yours is your own.