If you'll indulge me for a minute, I'd like to start with a personal story. I swear this is going somewhere :).
I'm visually impaired, and one thing I sometimes worry about is body language. This is because I usually don't see people's gestures, facial expressions and other signals sent by the way they stand or move sends. I've also been playing improv theater for a few years, and while I really enjoy it, I often feel hesitant to use body language, or mime certain actions. I also often feel unsure of how to interpret the body language of fellow improvisers, waiting for verbal cues to act upon.
In a recent improv course, I was asked to play a scene with the following setup: I was a man who, during his midlife crisis, "fooled around" a lot. My wife left me and entered a monastery. After some time I realised I had squandered the only thing that had made me happy, my wife, so I went to the monastery to try and win her back. When joining the order, my wife had taken a vow of silence, so she couldn't speak.
So I had to play a scene where my co-player couldn't speak. At first, I found myself falling back to what I know best, words. With someone who doesn't speak, that just becomes a monologue, which is not what you want for a 2-person scene. Physical interaction made things more interesting. When I went in to try to give her a hug, she backed away. This created a new interesting dynamic. After that I felt out of ideas on what to do. I got some very helpful hints from the trainer on playing with position; taking some distance or getting closer.
After the scene was over I talked about the uncertainty I felt, and had a very nice conversation with the trainer and fellow players about ways I could use the limited amount of visual information I had, and techniques to offer physical opportunities for developing a scene.
Taking part in this exercise, I felt incredibly vulnerable. I always feel like i can talk my way through every improv scene, and suddenly, that skill became useless. I felt incredibly supported by the others, especially after that conversation at the end, and it encouraged m
Often, saying "I don't know", and leaving your comfort zone are equivalent. You're comfortable with something because, at least to some degree, you know what's going to happen, and you know what to do. When you leave your comfort zone, you don't know what might happen, you don't know how to react, and you're afraid of being hurt or humiliated.
So I'd like to encourage you to seek out those limits in an environment where ou trust the people around you. If you're in a good trusting team, try taking on some of those issues related to parts of the code base you're not familiar with, or using a library you haven't used before. If you're in a great team, take advantage of that environment to say "I don't know" often.
Afraid of public speaking? Give a talk to share knowledge at your department or team. If that's something you really want to work on, I can also greatly recommend joining a Toastmasters club. They're a supportive community who'll give you constructive feedback every step of the way towards giving great public talks and presentations. I've seen people who joined our club in Maastricht, and go from trembling and using "um" every other word, to passionate speakers. They could only go through that change because they had the courage to say "I don't know how to talk to a group confidently."
So what narrow part of your comfort zone is holding you back? Look for a supportive environment where you can explore your boundaries, and see where you can expand them.