CG - you'll be OK. You just need to understand what's happened here. You had a big target to aim for, the R4L, and after (probably) a lot of effort and anxiety and anticipation, you achieved your goal (and well done for that).
What happens next is... nothing. And that's the problem. Most of us have had this problem. All our training is geared towards reaching some pinnacle, and when we get there, once the elation has died down we feel a sense of anti-climax and demotivation. This is often made worse because like you, we feel we need a reward and a bit of a rest. And we do need some rest and the chance to recover after a race, but this often means a few extra pounds, a loss of the running habit, slight drop in self esteem... it all feeds on itself and becomes a bit of a downward spiral.
That's the gloomy analysis. The good news is that it's not difficult to get out of the spiral. When you run first after a bit of a break it IS difficult. It takes, they say, only 4 days or so of non-running to start losing fitness. So the first run will always be tough. The second one will be better, and the third better still. By the time of the 4th you should be pretty much back where you were, and feeling great again.
Don't hate yourself for wanting to take a break for a few days or a couple of weeks. This isn't your 'nasty self' conquering your 'good self' It's just your body and your mind telling you that you've achieved someothing great, and both body and mind need a little time to recharge themselves, and get back the physical and emotional energy you've lost. It's all quite normal, and nearly all of us do it.
Just get out there and have a couple of gentle runs and in no time you'll be feeling gerat again, and looking forward to your next challenge. And that's the key - make sure you have something new to aim for. If your R4L was a 5K, perhaps you could aim for an autumn 10K? Or even a half marathon? Now that you've scaled one peak, you'll find it easier to get to the next one.
Good luck, and let us know how you get on.
Andy