I recently read an interesting point on expertise - the point being that if you are interested in becoming an expert in a field, it is not enough simply to repeat the same routines over and over again until you become an expert. A golfer does not become a champion by standing in the same place and repeating the same stroke to perfection. A car driver does not become a good driver just by going back and forth to work every day, and an artist does not become a good one just by painting the same type of image again and again.
If I want to be an expert, I should of course allocate plenty of time for the disciplines I want to become an expert in. But most notably, I will have to leave my comfort zone. I have to try something new; hit some more challenging balls from different angles; artistically experiment with more challenging subjects or with choice of colour; drive my car in a closed circuit to get out of the comfort zone without putting other people's lives and livelihoods at risk.
And I must accept occasional failure - and find an acceptable level of failure to avoid killing the motivation, without excellent results every time, as that would only indicate lack of challenge - and thereby lack of proper improvement.
(Translated from Udenfor komfortzonen efter ekspertisen)