Time passes, people change. Sometimes they change for the better, and sometimes they morph into these completely diverse people and you have no idea where the person you used to know so well went. In these cases you have two options: either fight to the bone to get back the person you used to know, and let disagreement widen the divide between you, or just accept the fact that the days you held so dear have gone forever and move on, keeping with you always the precious memories that will inevitably fade away.