During the winter months its very natural to feel slow, sluggish, and sometimes moody and borderline depressed. The season has a tendency to bring people down, which is why its always important to incorporate a heart-opening pose in your yoga practice. even if you dont do a full hour of practice, just opening your chest and shoulders with a single pose can work wonders to lift your spirits.
One of the best chest openers is Ustrasana, or Camel Pose. It lifts your heart towards the sky, and also allows for a back bend to strengthen your core. The only thing with this pose is that people tend to over extend themselves in an effort to drop back as low as possible. That is not the important part - lifting your heart toward the sky is - and it doesnt matter how far you can drop. With time and practice, that day will also come.
Below is a good demo on Yoga Journal
Hope you can do this at least once or twice a week especially during the cold season.
Here's to lifting your heart, and spirits :)