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You may be able to benefit from a full-spectrum lamp that you sit beside in the morning instead of the light box, plus getting outside on breaks. I've used light boxes, full-spectrum lamps, or tanning salons to get through gray winters with short days.

However, maybe you just need to cut yourself some slack while you focus on the tough part of the school term. Those sound like incredibly hard courses that require focus and a different part of the brain than you use for writing.

You could try getting up earlier and writing while you get your artificial light in the morning.

It's a basically a little box that makes full spectrum light (like sunlight). They are also called SAD lights.