There is nothing unhealthy about this. Your personality is your own. I am very much the same way only I get really upset or nauseous when I am around people or in crowds. I prefer to be within my own thoughts but I have trained myself to be able to get by long enough to work with other people and I actually work well with others and do empathize with others. I want to be a doctor and I know that it will involve being around others and I am fine with that because I know I have a passion for helping others. I am just not a social butterfly. I skip a lot of invites to hang out with others because it is just not my scene and I much rather do things by myself but I am a generally happy person. Laughter and joy will keep you living longer. No one can say for sure that being an extrovert guarantees that you will live longer in the same way that being evil or doing bad things will keep you alive longer because "good people die young". I think the situation is different relative to each person. If you like doing things on your own then go ahead! As long as you feel comfortable and happy doing it, you will live a happy life filled with peace.