He takes up all your time
Exercise is one of the best ways to grab some important 'me-time'; a much-needed break from work and socialising to gather your thoughts, get your heart rate up and burn off a few hundred calories. Then, suddenly, you fall head first into a sublime relationship and all your spare time quickly turns into 'me-and-him-time' instead. Of course you want to spend time together, and when faced with the choice between hitting the gym or being with your great love, it's not really a contest? Again, you should get into the pattern or working out together instead, or make it clear that your exercise regime has been ring-fenced and is not something that you are willing to sacrifice on the altar of true love. If he's the right one for you, he'll help you make time.