That is the wrong solution, watch out for this trap. Almost without exception, one or the other or both are bombing as a single person, they remember all the good parts of their marriage and compare it with how they are doing as a single and decide they would be better off if they were together. Then they remember why it was they came apart in the first place and it seems to get a little worse each time they come apart. It is crazy making. One of the things that happens when a relationship starts to go bad originally is that sex becomes poor, bad, or nonexistent.
Sex is normally sort of a barometer of the relationship.
Some say, well I got out of the relationship because sex just wasn't any good anymore. Actually, the sex wasn't any good anymore because something else had gone bad, resentments, loss of respect, etc. Lets forget all those other differences and get back together. This is all crazy making. Another thing about having sex with your ex is it keeps you from getting on with your new life.