From the age of 15 I had a side job as a re-stocker in a supermarket. I still remember how nervous I was when I tried to get that job. I had to go to the store, ask for the manager and inquire if he had any jobs available. This was way outside of my comfort zone.
For a couple of days I was very creative in coming up with seamingly credible reasons not to go to the store that day. But at the end of such a day I always felt bad about myself. So less than a week later, and very nervous, I went to the store to ask for a job. And got it!
When I was 17 and had worked in the supermarket for a couple of years, I saw a job opportunity working as a phone sales agent. It paid 3x what I made in the supermarket, so I applied. I passed the interviews and found myself sitting in an office surrounded by people who were more than twice my age.
They were all making cold calls to sell hotel stays, and I was hired to the same thing. Again, self-sabotage kicked in as my brain tried to protect me from lots of rejections. Years later I read that this mechanism makes a lot of sense from an evolutionary perspective. For a long period we were living in tribes, and being rejected by members of your tribe, whom you depend on for survival, is not a good thing.
I was unaware of that at the time, but started making calls anyway, and quickly found out nothing bad happens. Yes, some people slammed down the phone, but life went on. Experiences such as these taught me a very valuable skill: be comfortable being uncomfortable.
Most of the time you are uncomfortable your brain is trying to protect you from something you do not need protection from. What you are trying to avoid is almost always an area that would allow you to grow.
The bad news is going outside your comfort zone never gets easy. It is like jumping in cold water. No matter how many times you have done it before, you need to push yourself every time. If I am not tough on myself I start slacking.
What has helped is that I have cultivated the ability to be comfortable being uncomfortable, both mentally and physically. This post was actually prompted because I brought my daughter to school in the pouring rain this morning (she was dry and comfortable in the stroller), and I have spent the day with wet socks. Something I dislike which makes it good training.
But moving back to the mental, accepting discomfort / fears and doing things anyway is a good practice, and a key skill if you are in sales. Even if things do not work out the way you want, nothing happens. You learn something and life goes on.