How do you stop from being a jealous fiancé or girlfriend

By trusting the person you're with.

If you love you do have a tendency to get a bit jealous but if it's uncontrollable you have no trust. Just trust that your partner won't do wrong and you should be fine

Trust. Definitely hard to do when so many have friends of the opposite sex and some aren't respectful of them being taken. Been there done that...

I think everyone gets a little jealous sometimes.