Awww no don't feel guilty mate. I'm like that though ! One bite of a chocolate bar and if I'm outside my points I feel like I've done something terrible!!
You've lost lots already and I'm pretty sure you must have had an off day or two before this weekend (you're only human) and you've carried on afterwards. This time will be no different. Just start afresh.
I tell myself a bad day shakes up my metabolism to help me sleep at night !!