I have irrational fears, and they all go back to losing my father as a kid. I've never gotten over it.
Even if it is difficult playing with other people - sometimes it's great, sometimes it isn't, but that is kind of the point of it. It loses its point playing solo.
I think sometimes we look at other people's marriages and we think they must always be so happy together. I don't know anybody who's married for a long time who hasn't somehow made room in their love story for the hate and resentment that they sometimes feel toward each other.