I know others have hinted at this, but have you tried commuting? I try to commute by bike as much as I can, so I ride alone, but it's an instant motivator. There is no cutting the ride short and once you've ridden in for the day you've got to ride all the way home.

I almost always ride alone but it's mostly because I'm an introvert. I would like to ride with others, but I don't feel comfortable in a group until I really know people well. I'm aware of the character flaw but I want my hobby to be enjoyable, not some anxiety inducing event or something that constantly reminds me of what's wrong with my personality, so I ride alone. I guess it's also couple with the fact that there are barriers that I don't want to look stupid trying to cross (I don't know how strong of a rider I am, I'm probably not good at pacelines or group dynamics, etc.). I went for one small group ride, and it went fine, but it's just awkward and nerve racking, not sure I want that. The difficult part is that I know I'm not a weak rider, so I'd be bored going to a beginner no-drop ride. Probably be the equivalent of "over-dressed" too with a road bike and bike specific gear. I just don't seem to fit anywhere.

Incidentally, that's why I thought the clydesdale ride we were trying to get together here in Colorado was such a good idea. Some people in the same boat who wouldn't be judgmental and we'd all be recent acquaintances. Unfortunately I couldn't make the ride.