Many people in any company feel that being redundant to a particular work is a risk for them as they will lose the job. If any other resource does the same job then that both person would become redundant to each other which will risk for both the resource

Because of this 90% critical resource is not sharing what they know to their juniors or with other resources.
This has two side effects.

1. The company suffers
2. The resource will be going to comfort zone knowingly or unknowingly without even realizing that he is moving towards comfort zone. Everyone knows very well that staying in a comfort zone is dangerous for personal growth.

By the time the resource realizes that he is in a comfort zone, 90% of the time he is far from recovery from comfort zone.
In contrast, make yourself move towards an uncomfortable zone by sharing / teaching / letting others to do your tasks. Lets see how it will end up in personal growth.

If you share whatever you are doing, be it technical or non technical, with others (of course with the authorized person), will make yourself redundant for that particular work. Since the other person already knows what you are doing, you will never be in comfort zone.

In order to not to become redundant, you will push yourself to do new things which will keep you learning new things and keep yourself updated always

The above process to be followed in a cyclic manner.

1. Learn new things and master it.
2. Teach whatever you learnt to your reportees and enable them to do it. (This will make yourself redundant)
3. You will feel you are not in comfort zone and you will automatically go to step 1 which will be learning new things
The major advantage of the above cycle is that you will not only learn new things but also you will be get updated with the latest happenings and technologies