The hint that someone is not a dedicated teacher or a sensitive mentor lowers self-esteem and coerces others into making a commitment for fear of offending someone. Take time to evaluate your imperfections, the source of the criticism, and its intent before agreeing to do something. Desire for approval. The problem with saying Yes for approval is that soon those extra tasks become an expectation. When you take on more tasks to show how indispensable you are, you eventually burn out.
Insecurity makes people do unnecessary things out of fear of offending a supervisor.
Too often people say Yes to avoid conflict at all costs. They end up being a de facto martyr, and see themselves as powerless to change their lives, time management, space, or salary. There is nothing wrong with being self-serving so long as it is not at the expense of something more important in the long run. Picking up the slack. If no one else is willing to do these things, perhaps they are not worth doing.