Many individuals on the autism spectrum, and those with Asperger's, can be prone to depression, both the temporary feeling of sadness and the DSM diagnosis of Major Depressive Disorder. Of course, I can't treat mental health issues or diagnose over the internet, but I can direct you to the well written Mayo Clinic website. They discuss Depression, nutrition, Seasonal Affective Disorder (SAD), light box therapy, the benefits of exercise, psychotherapy, and even alternative therapies. My favorites are the coping and support sections under the topics for both SAD and Major Depression. These are some excellent tips for improving your moods, and taking steps to feel better. The site also has good info on when to see a doctor.
If you're feeling a little down after the holiday rush, why not check out this website?