I have the same problem you do. If I put myself in a competitive state with weight loss I have no problem staying on plan because I HAVE to win. Once the competition is done, I fall off the wagon...because there isn't anyone to beat anymore.
So I've slowly had to train my brain that I'm doing this for me, not because it's a competition, not because theres a huge prize at the end, or the victory of beating my competition, and that this isn't a race. It's because in the end the ultimate goal is...being fit, and healthy and thats what we want right?
I don't really have a support system or much help I just do it on my own. I also have a friend who wants to lose weight (so with our eating we're supportive, but our workouts we enjoy two different things.) You have to be able to do it on your own. Sure it sucks not having that buddy system but in life you don't always have a buddy system sometimes you just have to do it on your own. This is one of those things. Don't think so much about it, just go do it. Get back to the gym (or however you were working out) and just stay on track with you meals.
You've seriously have had amazing progress and a great loss. Don't lose sight of that just because it's now just you.