It is said that nothing great ever came from a comfort zone, that a person must be stretching at all times to get to that next level regardless of their field. Only by moving outside of your "comfort zone" can you expand your learning and move on to greater things in life, etc. In my limited experience I have not found this to be true and find it a load of crap to be honest.
First off, I hate that term "comfort zone", it has always irked me to the point of throwing something at a wall, it is lazy psychology and is thrown around in work environments as if it is something to avoid at all costs.
Managers skulking around like boogeymen warning that performance levels may drop if you even dip a toe into the forbidden comfort zone.
People are somehow convinced that performance is intrinsically linked to people being comfortable and for some reason they are under the impression that you will somehow perform better if "pushing yourself". I firmly believe in the opposite, I think that people work harder and are more creative when "comfortable" and are confident in what tasks they are performing.
This is not to say that you can just kick back with your feet up, I put more than two years working 15-18 hours a day into Avalanche and that was just to build into a recognisable brand and gain some market share. It is hard work especially for those who choose the entrepreneurial path to do anything noteworthy.
Everybody has a comfort zone in all aspects of their lives: work, sport, socially. It is from here that people have ideas, make friendships, learn to drive a golf ball an extra 50 yards. Instead of trying to get out of a comfort zone, a person should try to expand their zone to the point where they become fearless in trying new things, starting a new side-business, trying that 50 yard pass instead of a 5 yarder or even talking to that pretty girl (On the internet doesn't count!).
Personally, one of the things I have always hated is public speaking, I get invited to give speeches all the time on my experience of being a young entrepreneur and how I achieved my "success".
The majority of the time I reject these invitations, not because of a fear of public speaking or anything like that but because I struggle to understand why anyone would want to listen to me waffle on for an hour. I have told myself that I would force myself to go to a few more of these things in the coming months/years as I have received good feedback from a couple of people leading me to want to build the skill.
I find there is a big difference in wanting to get outside a comfort zone and grow a useful skill to the point it becomes second nature. I would advise people to try and expand their "comfort zones" and increase their skillsets more than the ridiculous notion of trying to get out of their comfort zones.
Stay comfortable, stay working.