The hardest part

Dieting has been going really well so far and for the last 5 months I've managed to stick to the weight watchers plan every day. In a couple of weeks I'm going on my first holiday since starting dieting and it's going to be really tough to stick to it. Apart from the fact that temptation will very much be a factor when I'm away, I wont actually be able to calculate or track anything I'm eating. Coupled with the alcohol factor and this could be the first week I actually put on weight since I started dieting.
I'm not going to let it affect my holiday since I want to be able to enjoy it as much as I can but here's hoping I don't put on too much...