People also suffer from SAD at other times of the year. This could be determined by seasonal changes in a person's life growing up. For example, if you spent the summer in a stressful environment growing up, the distressing feelings can return at that time of the year. Or the feelings related to a tragedy, or significant loss that occurred can be "relived" at that particular time of the year. Also the symptoms can be different. Some people report feeling manicky ('hyper', obsessive, grandiose or rapid thinking, increased gambling or drug/alcohol use, pursuit of superficial relationships, excessive spending ). If you experience such symptoms to the extent that they interfere with your life (and it can get pretty bad, sometimes requiring hospitalization), i.e. your relationships, job, overall happiness, then you do need to fix it.
Light therapy is recommended as a treatment based on the theory that the decreased exposure to light in the winter influences certain brain chemicals that trigger depression. Even exposure to increased sunlight (like at the beach) can be helpful. I often suggest that people try St. John's Wort, which is an herb used to treat mild to moderate depression, and symptoms of stress. Some have had good success taking this in tea, or pill form. Psychotherapy helps, as may medication. To "fix it" long term, you should consider some lifestyle changes. Preparing for that time of the year (winter or other times) is very helpful. Try to reduce your overall stress levels at that time; have supportive people and relationships in your life; exercise; plan enjoyable activities; be aware of early signs rather than waiting until you're in the middle of a depression before taking action. Don't miss out on the happiness that you deserve, and is so important in our lives, not even for a few months.