We all go through painful and frustrating moments. All you have to do is look around yourself to see this. Everyone has hard problems during some times.
The cause is our attachment to the familiar, the known.
We can still have meaningful relationships but without that needy, clingy attachment based on fear of loss and fear of being alone and separate.
We stop expecting things to be a certain way. We stop rehashing the past because we are focused on right now. Not torturing ourselves about things we did!
Wee need to see things as they are.