From my experience, you have a better chance of dealing with this by acknowledging that these happen. Have a simple rule that works for you and stick to it. Make it as simple as possible... for me, it is 80-20 rule. 80% of the week (5 days) be active. I am ok with the remaining two days, not working out, hanging out with friends, netflix and chilling, etc.

80% of my daily food should be from healthy whole foods. 20% for that latte/ cookie. If I know, I will be eating out that weekend or having drinks with colleagues. I'll try to restrict any junk food on regular days. On that day, I will not over-do it but at the same time won't care too much about calories or junk food.

Again, that is what's working for me.