Just why is it that parents always have to invade the life of their children?

Just last night I was talking to my mom about a sensitive matter involving my girlfriend. I told my mom that I am gonna break up with her because I am not happy anymore, i don’t want to force myself. Then she all gets mad and furious at me. Why can’t she get over it? I am 21 for the love of god. Can’t I decide on my own?

Do you guys happen to have any issues of the likes?