The capacity to endure a more or less monotonous life is one which should be acquired in childhood. Modern parents are greatly to blame in this respect; they provide their children with far too many passive amusements… and they do not realize the importance to a child of having one day like another, except, of course, for somewhat rare occasions.
Talk about mundane moments when your mind is not fully engaged with yourself. You can’t focus. Or you have lots in your “to-do-list” but not in the mood to get started. I, myself often experience this and call it boredom. (I slap it on the face!)