Forget it.
Get back on the wagon right now, drink lots of water, if you know 9pm is your weak spot do something about it - a walk, a bath, do your nails, make a hot drink - just get cracking and forget about what you did.
And if you DO manage to get away with it, don't do it again thinking you'll be ok again, you won't. You'll just slide down the slippery slope even further. If you reel yourself in now, you've a chance of getting back on track.