How do you help your partner gain trust back?

Sometimes it just takes time. Sometimes they never gain trust back if you have given them a big reason or many reasons not to trust you. Also, there are some people out there who will never trust ANYONE because they themselves are not trustworthy. For example, I know of women who "get their man" by purposely getting pregnant and trapping the man into marriage. Then the woman makes the man's life a living hell because she doesn't trust him in anything he does. She is always suspicious of him and distrusting because she knows that's the way she is and she assumes he is like that too. Deep inside she knows that she had to trap him in order to get him instead of getting him because he really wanted her and wanted to be with her. I know of men who are always suspicious of their wives running around on them but it's oftentimes because the men are the ones doing it and they think the wife must be doing the same thing. Then there are people who have just been burned so many times that they trust no one really until the person EARNS their trust over time.