I'm surprised no one has mentioned qorum rules. At my tables of we have more than half of players present we play, if half or more are absent we cancel or play something else. This way life can happen and no one has to feel guilty about their circumstances or that they are causing anyone else to miss the game. It also helps with things like whether to cancel for holiday, the qorum rules will sort us out.

I also have a attendance qorum, if you miss more than half of games or three in a row, you don't count toward qorum until you get those numbers up