As soon as you wake up, open all curtains and blinds- any light is good light.
Maintain your routine- don't neglect your hobbies.
Get outside- dog walkers have to do it.
Ditch the sugar- sugar feeds depression.
Develop wintertime interests- become a super-chef, a knitter, a blogger, a singer, a dancer.
Practice relaxation- breathing exercises, yoga, mindfulness.
Watch a funny film- it is hard not to laugh.
Keep warm- hot water bottles are great, hot drinks, warm socks.
Keep working out- you will feel better even if it's a struggle.
See friends and family- they might need cheering up too.
Book a massage- a study shows massage appears to increase your brain and body's level of serotonin.
So, don't hibernate, you are not a hedgehog.