For me, being out in freezing temperatures below -10°C is a way of training the body to keep its comfort zone broad enough. Having expanded the comfort zone towards lower temperatures gives me -- as the word implies -- comfort over a broader range of days throughout the year. As soon as I stop doing this, the comfort zone shrinks and, as a result, the amount of days in a year within my comfort zone shrinks as well. I love winter wonder days like today in Stockholm.
