First and foremost anything extreme is out of the window.  Nothing drastic needs to occur to balance out the night out or weekend of having fun.  

We just need to build back in some good habits.

That means:

1. Getting to sleep and catching up on some z’s; feeling like I have had a good nights sleep makes me want to make positive health choices and move more.  The temptation when feeling off colour and of low energy is to grab the fast food and high calorie drinks to make it through.  If I don’t try and correct this, then I will be making poor convenient food choices and sitting about a lot more and for a lot longer. 
2. Each night I have made an effort to be in bed close to an hour earlier than normal, sleep is the best medicine for recovery!
3. Sensible food choices: no huge calorie deficits or restrictions, just try to implement some simple dietary habits such as three meals a day and a couple of snacks.  As part of the meals try to increase the nutrient quality, I’ve added more fruit and vegetables.  
4. Move: At the start of the week, training was not at the top of my list or even half way down.   I just didn’t have the energy for it.  So my first training session was mid way through the week and I didn’t try to max out any weights, I just tried to limit rest periods and keep moving.  Prior to this, I have tried to cycle and walk when possible.

As you can see, nothing radical here.  A big aspect of such a weekend like this is that they are very infrequent.  

If going out every weekend was something I did, then more drastic changes might be in place or even a change in my goals as realistically I would not be obtaining them with weekends that would send me off course so frequently.

I am a big believer in flexibility and moderation, so enjoying weekends like this with good friends are almost a right of passage.  Enjoy them and ease back in to those good habits you created prior to such a weekend.