Backsliding

[Sarah]

To go back to talking to, dating, or having sex with a previous ex. The backslider tends to be the person who broke it off, but not always. Friends must watch out for their friends who may be backsliding especially with those who have had a recent break up and/or if they don't think the two people should be together.

[Oralee]

Backsliding is the [action] of [crawling back] to ones [ex].{Very popular}

[Couch Potatoe]

The action of relapsing into bad ways or error.