I think that its a learned behavior is very possible. I grew up where I was mistreated (that's really an understatement) and I have things that are sort of "automatic" reactions to situations, though I do not let myself react-I generally hold it in and go in the other room, for example. When your 5 year old is driving you nuts and you want to react, try taking a time out for yourself, even if it means his behavior isn't immediately addressed. That way you have time to calm down and come up with a rational response. Its hard having a child, I was a single mom until my son was 4 1/2; I know how much that can push your buttons without even meaning to.