Do not get hang up on your past.
Do not nag or distrust your current boyfriend just because your ex hurt you. Do not treat him or the relationship the same way. Do not compare. He will not react the same way as your ex. Do not be worried that your simple mistakes will cause him to look for another girl. What happened with your ex was not your fault. It was not because you didn’t guard him enough or you didn’t make him happy enough.