What you describe seems like Seasonal Affective Disorder (SAD). I have dealt with this for years, it is the diminished sunshine during the winter months that causes it. There are different therapies available, one is a SAD LIGHT BOX that gives you full spectrum light that replaces the sunlight that isn’t present. I have used this with varying results. The one thing I found that truly works is to head south in the winter and go some place that has sunshine almost everyday. For many that is not an option, exercise does help in that endorphins are released in your brain and that seems to brighten things. I take a “brain medication” already for anxiety but that does not ward off the SAD, it is a real problem come winter. God Bless!