First, use bright full spectrum lighting indoors whenever you can and spend time exposed to it. Second, go outside during the day when the sun is shinning even if it’s just to sit in your car with the motor running and the heat on.
The key to combating SAD is light exposure to a full spectrum that is and/or mimics the Sun for some prolonged period each day.
Humans have rodent DNA from our evolution that makes us want to hibernate in Winter. Since we can’t, the key is light to counter-act that desire buried deep in our genome.
