Even though couples are comfortable with each other, he or she must at least stay fit for themselves. Sure, people feel comfortable around each other, but sometimes they must do it for them. I have been in 2 long term relationships and the latter being married. It never stopped me from working out. Maybe I was always in athletics growing up, so it must be a routine thing. Most of friends have let themselves go physically, and some do feel bad wanting to make a change. Everyone's lifestyle is different; busier lives along with obligations does make it hard to fine time for the gym. But hey, if there's a will, there's a way.