You won't lose yourself or your personality... unless you choose to change something. I'm still the same person I was before. Same likes, dislikes, values, and preferences. Never liked chocolate, still don't. I find the hardest proposition during transition sometimes is not just convincing yourself of this idea... but others. Even close friends and family. They think that since you may look different, you are a totally a different person on the inside. Which couldn't be further from the truth. Your life up to this point, past, history, and accomplishments have shaped and formed you in to the person you are today. No amount of meds or surgeries will change that.
As a side note: I never ascribed to the whole my "male name" had to die so my "female name" could live. Some aspects of ones behavior, personality, even your legal name & gender might change... but at the core and as a whole, IMHO & IMHE, we are still the same people. We may change and adapt, in a somewhat drastic fashion... but the death of one's identity, is something I don't agree with regardless of transition. Your identity made you who you are and defines you as a being. Male, female, tall, short, gay, straight, etc. are labels. Your identity is special and unique to you and needs not conform to societal labeling.