My complexion looks duller under the winter sun... What's your whitening routine?

I was determined to diet and travel in the new year, looking slimmer... but last night, I couldn't resist temptation and ate a ton of bungeoppang (fish-shaped bread). Feeling depressed, I looked in the mirror, my resolve broken. My skin tone became more noticeable than my weight, and it was truly chilling. Unlike the clear, cool air of winter, my face felt parched and dull from the heater wind. Isn't it especially important to find a proper whitening routine in times like these? Maybe it's because the morning sunlight pouring in outside is so clear, but it's frustrating how my skin looks so dark. I'm curious to know if everyone has a whitening routine they stick to to maintain their radiance, even in the winter. I'm currently using just one vitamin ampoule, but I'm worried that my blemishes aren't improving much. Should I add another sheet mask or consider another method? I'm starting to feel a bit anxious, wondering if my whitening routine is lacking synergy. Am I being too greedy for my skin to maintain clear, snow-white skin? Could you share any tips you've found effective or any must-have products you'd like to recommend? I'd love to hear how others are solving their skin tone concerns, even if it's just a small story.