It is normal to feel uncomfortable at first when you leave your comfort zone. It takes time and perseverance to get used to new situations and challenges. Persevere and realize that this feeling of tension is a sign that you are growing and experiencing new things. When you step too far outside your comfort zone and the fear becomes too great or when you block and don't know what to do, you are in the "panic zone." So the key is to incrementally increase the performance zone and with that, the comfort zone will naturally grow along with it.