What are some of the signs that you are/were about to be dumped?

I was only dumped one time as a teenager. I still do not know why I was dumped. Today, many male and females are dumped. Maybe some of you, like me, did not understand why you were dumped. Question: what excuse(s) did you give or receive, from or to your bf/gf, that has lead to a breakup in your relationship?