Maybe it's better to think about what did happen that was good, or to be more flexible. Like if someone did hold you or cared for you for a time, wasn't that good at the time? It was something good that happened in your life, even though the person left and or even didn't care later on. For that time you felt great, it made those days better. All we seem to think about is how it ended.
Maybe there would be a lot more holding and caring going on in general if we could just take what we can get, not requiring that the other person sign a contract to always be there and keep doing the same thing for the rest of their natural lives. If someone will hold you and care for you today, even if they leave tomorrow, at least it was something good that happened as opposed to more of the same nothing.