I have to disagree with a lot of the posters on this. I think that if you had a very close, longer-term relationship with someone, it’s best to have some closure. Both sides should be given the opportunity to vent and/or decide if they want to continue with some kind of post-relationship friendship. Many of the people I’ve dated weren’t for me right in a romantic sense, but ended up being pretty decent friends. I know a lot of people who’ve maintained good friendships with exes.
