Break ups and 'crazy exes'

Some questions I have been asked about relationship break ups. Also, if you cannot get over a break up, does it mean you're a 'Crazy Ex Girlfriend'? Is there a “normal” length of time to get over a break-up? Why do some people find it harder than others to get over a relationship ending? Does your general mental health have anything to do with it? How much does the circumstances in which a relationship ends contribute towards the recovery of a break-up? I'll tell you what I know about heartbreak . . .