Don't we all have insecurities?
Talk to people who break up. The dumper or the dumpee. And I promise both will say the other was insecure. Aren't we all insecure. No one wants to be rejected for who they are as a person. Everyone questions their place in life. Some people who can appear to have everything end up committing suicide. What people should say is, that particular person's insecurities are incompatible with mine. We are all looking for someone who doesn't exploit our insecurities. Someone who understands without explanation. A lot of people who post on this board aren't any more insecure than their partner is or was. They just weren't ready to throw in the towel. Sure, maybe your quirks irritated them and theirs didn't bother you but what can you do?