Here is how the "double-fence" is supposed to work.
One makes a condition that when he has an urge to act out sexually he must first do a,b, or c (say one kap. tehilim, give a little zdoko, call your grandma) and if he acts out anyways, then he gets a knas which is substantial but manageable.
However, (second part of the fence), if one acts out without doing a, b, or c, then the knas he must pay is heavy to the etxent that it serves as a serious deterrent. Of course honesty is required.
In other words, you promise yourself to not act out without doing something first, which puts some distance between you and the act and shows effort on your part. You're then free to act out if you still want to: but then you must pay a knas, so it's not a "I already said tehilim I might as well act out".
But if you lazy out on the first condition then you pay a much heavier knas, like sayong all tehilim or driving to Miron and spending the day there ( I know guys who;re doing something like that).
All this is described in the Taphsik section of the gye website, I just omitted the swearing part.
Good luck, you're showing some hard work.
Mottel