There is rarely a valid excuse not to sketch wherever you are, any time night or day, alone or with companions.
Grab it while you can, working from life whenever possible. Imprint the image in your mind. The contour sketch done on location will trigger the memories, the sight, the sounds, the fragrance, the mood. Later, settle down with a cup of tea or a glass of wine and work from your visual memory to add color to the contour drawing. This is a wonderful workout for your brain, strengthening your ability to be creative based on real experiences and making the marks your own. The bonus is that it is fun!