The old phrase in the title of this post “if nothing changes, nothing changes” is relevant regarding your personal satisfaction and development. If you do the same thing, day in day out, whether it be in your personal or work life, you quickly can become bored, and pretty soon boring, as you lose your inquisitive nature and interest in other things and other people.
From a career perspective you may remain employed but cease to be employable which is of course dangerous and livelihood threatening if one day you do cease to be employed. At that point your lack of depth and breadth of skills and experience may make it difficult to find a new role.
Think of your comfort zone as a matchbox containing your knowledge, skills, experience and capability to perform a role. You are confident of performing well in situations within the matchbox as you have the capability to do so.
Imagine that over time that you swapped that matchbox for a large wooden chest, which is deeper, broader and higher than the matchbox and so contains much more in the way of knowledge, skills and experience.
Obviously you need to work on developing proficiency in these new skills you have learned and be able to apply them in a range of different situations. However, assuming that you do, then over time you develop the capability to confidently and successfully perform in a much greater range of tasks and responsibilities. This adds to your own sense of satisfaction and wellbeing and enhances your confidence to take on more. In turn you become more employable for a greater range of positions in the eyes of your current or future potential employers.
To extend your comfort zone just decide what additional knowledge skills and experience you want to develop and then set out to acquire them. In everyday life, as in the workplace, look for ways to do and experience new things and to learn to feel comfortable in being in new and uncomfortable situations. Over time you will develop a mindset where you are continually seeking to “test” yourself either by trying new things or using your existing knowledge skills and experience in different situations to enhance your existing capability still further.
Overall, remember that if nothing changes, nothing changes.