As the first part of the word comes from Greek misos = hatred it seems a bit odd: a happy hater.
We use a word straight from German : einzelganger (from Einzelgänger) that has a neutral connotation. There are pleasant as wel as unpleasant "lone-goers " and it could be disputable whether happiness should be a permanent state of being or just returning moments.

Cheers from a non-misanthropic einzelganger and HAPPY New Year!