Hi, I can totally relate to where you are coming from as I too work a lot in Africa. There is nothing worse (aka more tempting) than being cooped up in a grotty hotel room with noone to be responsible to, together with the availability of lots of cheap booze and a terrible/non-existent internet connection so you are bored stiff. My solution now is to take a portable kettle and lots of tea bags, hot chocolate , powdered milk, soups etc so you can have something else to drink. I also make a point of downloading lots of films and TV programmes before I go (the internet there is likely to be so slow you can't do it ). I also take boxed sets of DVDs... so I am then quite happy spending an evening drinking tea and watching a boxed set of Homeland or similar. I tend to go to places that are a bit dodgy eg DRC so you can't really go out .. but if you can, then hang out with your colleagues, go to the craft market or beach or watch some live music... all that can be great fun ! In addition I also tend to work in Muslim countries which is a great bonus as folks then don't drink anyway ...:-)
I TOTALLY know where you are coming from but pack your bag with tea and DVDs - get the Lonely Planet or similar and find interesting trips to do at weekends, the hottest places for music etc and time will fly !
Good luck !