how can you convince yourself NOT to be jealous
you can't. plain and simple. if you're jealous unless something happens (person gets disfigured and you think they're ugly. you find the "right person" and are happy with him/her and never even put thought to anyone else shit like that) if you're jealous that's all there is to it.. it's always going to be in the back of your mind... and that's what seperates the type of person you're asking about. some are just able to keep comments/questions stemmed from the jealousy quiet, and can act completely normal around all persons involved, and some.. well just can't keep their mouth shut.

short answer you can't control it, you just choose rather or not to ignore it.