Once you have decided to move on, you must understand that your former partner owes you nothing. Closure is a myth we like to "go for" in our breakups, but closure is up to us as individuals.
The goal is never to blame the other person for the breakup, even if they were the reason you are breaking up. Always take your responsibility for the miss. And make it about the chemistry, the mix, the overall relationship and not about them or their poor behavior. Remember, you are leaving the relationship, not trying to teach them a lesson or educate them.