I've often found that, at least for me, I have the urge to fall or indeed I do fall at the absolute worst times. Whenever I'm about to be doing something fun, or ive just finished something fun or I want to be clean for a certain occasion, that's when the hardest moments are. I'm not sure why its like that, but even today I someone showed me a funny, clean, video clip and we both had a good laugh. As soon as I was alone again I had an incredible urge to fall. I think there is even a biological reasson- when you fall, your body releases a tidal wave of chemicals that make you feel great very briefly ( the guilt crash comes after these chemicals are depleted) so when your brain releases only a little bit, your body which wants the tidal wave that its used to, acts up. Anyway what I did when I was about totally was I told myself ' just be happy with this good time you had, you don't need anything more' I think its important to recognize the times when the desire to fall comes, which are often when you absolutely least want it to ( like in shul waiting to daven). Those are the times you need to be especially vigilant. You CAN do it!!!! Good luck!!!