Does a persons personality go through phases?

lately(past couple years) i have been extremely introverted. i don't necessarily dread socializing just prefer not to .my girlfriend and i broke up almost a year ago and suspect it might have something to do with my current state. so basically i am curious, am i just laying low for reasons unknown to me? is the current state of my personality a permanent or temporary? is my subconscious "protecting" myself from being hurt or hurting others? any comments would be greatly appreciated.