Well I had such problems in the past, what I'd do is to meditate
(easier said than done) and keep pyscho-ing myself:
"This is your time, nobody and their activities are of concern
to you, your commitments are also of not concern at this time. This
is your time, this is your time to be of use to you only, this is
not their time... (repeat ^ repeat)"
Basically allowing to re-balance your emotions, especially after
a year's of bitterness or something (I WAS BITTER).
Eventually I rationalize that christmas are not celebrated
universally (i.e thailand), the rest of the world still goes
on as usual in christmas, doctors are still saving lives, clerks
are still working, shoe peddlers are still peddling
shoes, bootlickers are also bootlicking, why should I be
worried about celebrating some day that I have little relations to?
(I am not a christian.)