The idea that someone who is miserable, or in a bad situation, will try and pull you down with them, so that they don't feel so alone, or like they're worse than everyone else, or whatever reason. Maybe this is why so many people feel that that it's their mission in life to make sure everybody is drinking and doing drugs just like they are.

Some of us circle aimlessly like moths,
Buzzing bewildered around a light:
We're bound so valiantly for the moon,
But smash ourselves senseless each and every night.

Some of us are like crows perched on a wire,
Watching the world pass by down below:
Birds of a feather, we flock together,
Because it sure beats being alone.