Trust is based on the emotional investment people place on the other person.
A good healthy relationship has a balance of independence and reliance. It sounds easy on paper, but can be difficult to live, and hard to see when in the relationship. A good philosophy is only to 'trust someone if you are prepared to have them let you down'. Some people think this is pesimistic, but it is in fact empowering. If you can accept that the person could 'betray you' whatever that may be to you, the fear goes and if it happens, there is better coping.
All these long convuluted stories of he did this, and I did this and he said, comes down in the end to being with someone because they compliment you. If you have a fear of being alone, it is a seperate issue and you might as well give trying to be objective as the victim is your role in life.
But if you have the confidence in life to be on your own and only have people in your life that make you feel good about yourself, these issues can be managed through boundaries being established, consequenses for failing these and in the end being prepared to find better people to be in your life.