You feel that way because that's what you're used to. When you get leveled out, you do feel like someone else, but you don't know who. That's totally normal and actually a very good sign that you are stabilizing.
It will definitely take some time to adjust to the "new you", but your family and friends will love it. If you still have the same interests as you did before, (I didn't, it changed overnight), pursue them, it will give you a sense of identity. If you don't, try to think of things you might enjoy doing. Start excercising, it will make your mind feel much better, not to mention the body. I bet there is a beautiful person in there wanting to come out, not a moody, ragey person to tiptoe around. (Assuming your mania was to that extent).