In certain cases, sex with an ex is sexy and fun and exciting. Temporarily, that is. I have to believe that nine times out of 10 the after effects are disappointment, hurt, sadness and regret. So, be careful.
Rule 4: Have Somewhere to Be. It feels good having somewhere to go. You don't have to be specific, you just need to have somewhere to go. If you don't have anywhere to go, don't make up something too far-fetched, like escorting a movie star to an awards ceremony.
If you had a very good sexual relationship with your spouse, despite the fact that you absolutely couldn't live together as man and wife, it does seem a shame to give it up altogether. Great sex, is, after all, great sex.