In human life the cause of all difficulties, all discords, all moral sufferings, is the presence in everyone of the ego with its desires, its likes and dislikes. Even in a disinterested work which consists in helping others, until one has learned to overcome the ego and its demands, until one can force it to keep calm and quiet in one corner, the ego reacts to everything that displeases it, starts an inner storm that rises to the surface and spoils all the work.
This work of overcoming the ego is long, slow and difficult; it demands constant alertness and sustained effort. This effort is easier for some and more difficult for others.
Ref: Words of The Mother Vol. I