Maybe you should ask yourself if you really lost you at all? Moving out of a serious relationship is bound to cause a shakeup in your lifestyle and emotional state. We're supposed to be different in a relationship as it has it's own challenges that we have to rise to. I'm not saying you become a different person intentionally to please someone else as that isn't happy, but you should expect some changes. At the same time, hopefully you haven't totally disregarded your own personal interests and hobbies over the last couple of years so that you have something you can still cling to and find some joy until you get over the emotional damage.
Also, like others have said, don't let your current state cause any deep scarring and bitterness. Being in a relationship will always mean you have to be vulnerable. If you aren't willing to do that again in the future then you won't have learned anything. Learning to protect yourself isn't really the goal here, but rather learning how to make sure future relationships are better protected while not giving up who you are, and also by learning how to better pick who you allow yourself to enter into such relationships with. Still, there are never any guarantees since all people have free will.
Hope things work out for you. In the meantime, stay busy with things and people you enjoy.
