It is especially cold this winter.
I have an idea to make yourself warmer, when you are , for example, waiting for a bus at the station in the cold wind.
You might have a handkerchief, or empty plastic bag, or some string in your pocket.
Make a knot with it and pull it tight, And then loose it. Repeat this. If your nails are too long to deal with the knot directly, you could use a pen or such stick to insert into the knot.
To press something hard with your fingers seems to need a static power from all over your body. In addition, you will be excited if the knot is too hard, that also make you hot.