You need to not play involved games.

LoL
DOTA2
MW:3
BF3
CS:S

etc., etc. These are all games you can play with less than an hour of time (LoL and DOTA2 are really the only ones that "require" a certain block of time). You can quit at any point without others getting pissed at you or you feeling like you "need" to stay. That's why I will never play WoW again; it requires me to schedule time to play. That and other reasons, but that's the main one. I can't just pick it up and play for an hour when I have a free block of time because you can't get anything done in WoW in an hour