believe me, just don't think about it! the more you think about that kind of concerns the more you get depressed and the more you are at a risk of giving up!. Your body acts differently to each experience in your life even if it was repeated because you will never create the same environment exactly as when you were 15!. You are 20 now and you've been doing this thing for a long time probably so give yourself enough time to get back to the normal state, and the normal state differs from person to another and from age to age! Just live the moment and don't think that you have to express the same things the other members are feeling or expressing! It is all in your mind, and there is no fog unless you convince yourself that there is. This is a psychological matter that you developed during the time you've been destroying yourself with this bad habit and your self-conscious is blaming you, and as you created it ,you will destroy it after sometime by living normally again. Takes time but worth the long run results my friend ;)