This is actually about the fear of rejection. Especially in long distance relationships. I am in one myself, have been for some time. It is my belief, and this is from both sides. We are always fearful of the possibility that sometime during our relationship, whether it is an actual bf/gf, or just good friends. We are going to get the dreaded Dear John/Jane letter.
It is hard to ignore our own need to be directly involved with the one person you love. When we cannot be there, we start to wonder if someone else may be trying to step in. It is human nature to want contact with loved ones as often as possible. It is also in our nature to wonder and to worry. To hope and to pray, to desire and yearn. However, I feel, the very fear of losing the reason to do any or all of these is the very thing that can kill a relationship. When people get to a point where wonder and worry get to be too much, we may end up dealing the very hurt we fear.