I've experienced this too, not just in winter. I live in Scotland, and the weather is mostly wet and damp (rain on ~2 out of 3 days of the year). This year we

I've experienced this too, not just in winter. I live in Scotland, and the weather is mostly wet and damp (rain on ~2 out of 3 days of the year). This year we had a glorious summer. I got productive work done in a single month in June than the entire first 5 months of the year.