I have a bit of a problem with this advice!  Quite honestly if you are in a relationship you should not be entertaining meeting secretly with another person and exploring love -v- lust!  Too many people end up in my office because they have not focused on their relationship.  Couples stop communicating, stop paying one another attention and stop showing an interest in one another.  This is what you call "working at your relationship".  If you don't want to do it end your relationship before looking for another love interest.