There are many times I believe that I am the only person who can do the job. It is a bit self aggrandizing, but when the rubber hits the road, there are others who are just as capable. Do managers, et al have this impression that they are the end-all be-all at work?
It is presumptuous to think that this is so, but we as managers all have this feeling that the world will stop spinning if we do not have our fingers on the pulse of what is going on. The problem is if you do not let go and delegate, you will become a self-fulfilling prophecy. Staff will come to you for every answer. They will not make any decisions. It will be up to you to solve every problem. This will stress you out.
In order to not be the Wikipedia for your department, you as the manager need to recognize that there are also people in your department who can also answer the questions and also do the work. It is nice to think that you can be used as a resource, but not letting your staff make the decisions on behalf of the department takes something away from teamwork.
While the responsibility ultimately rests with the manager, it is nice to know staff have the autonomy to make decisions and be thinkers for the department – providing you as the manager is willing to allow them to do it.