Most Helpful Guy
Do what most people in society would do.
Think with your genitals first and your common sense second.
Most Helpful Girl
It depends on why the relationship ended. If there is a solid reason why (someone cheated?), don't let yourself forget the reason why and the tension will go away. If the breakup was mutual for less solid reasons (just not fully happy...) it might be good to talk to him. Just pull him aside and talk about it and then move on (or lay down if that's your approach! Lol)