I think when you find the correct person for you the jealousy goes as you know you can trust them and if your 100% happy then you generally trust yourself as the need to "check out the menu" goes. I think the latter leads to the first. Don't take anyone back after a break up, as they say a leopard can't change it's spots. People always do it and then break up again. You've gotta remember why u break up in the first place, people forget because there emotions get the better of them. Things may change for a while but will almost always return to the way they were.
Met my missus at 15yrs old, 100% happy and content ever since!
Ps I think I should get a forum on here lol agony uncle haha