Gut, maybe you could join a club or something and get out more. Or invite friends over for dinner or a glass of wine.
Take a class. Do something for yourself that you've put off doing because you had kids at home. You need to get out of the rut of getting up, going to the gym, going to work and coming home. Get something special going that you look forward to doing once a week or so.
You could always ask Dan to come back. (just kidding)