But since Samhain (the usual time of year my seasonal depression begins) I have felt my energy slowly depleting, as if I'm spiritually treading through quicksand. I am to the point where I feel I don't have enough energy to even make a shrine to the God and Goddess and give thanks.
Have you tired bright lights? They reportedly have a positive effect on many people who find the winter months depressing? It might be worth talking to your doctor about this as there are certain intensity levels and schedules that are needed for it to be effective.
In any case, you will be in my prayers.