When they're in their own misery, nothing else can bring them down, since they're already at a low point. The last thing that they want is to be brought down even more. So the safest place they can be from that is in their own misery.
What makes you certain that any particular person does enjoy his or her misery?
Thanks for clarifying.
Maybe that's all they know.
Misery isn't fun, that's why its called misery instead of happiness. People get stuck there because its easier than trying to be happy and have that door slammed in their face again.
They're weak minded individuals