There is no part of life that does not contain lessons. If you are alive, there are lessons to be learned. Does it ever seem like just you have mastered one lesson, another challenge present itself almost immediately? Just when you get what it means to posses self esteem, you are faced with a lesson in humility.
As soon as you get what it means to be good Parent, your children leave home and you need to learn The Lesson of letting it go. You figure out one day the importance of having time to yourself the next day you are called to support someone else striving to get all the details of life under control is impossible, because life will present a new lesson daily. You never actually finish all your lessons for as long as you are alive, they are lesson to learn. Regardless of your age or station of life, or success level.