Exaltation

In my opinion, exaltation involves the work of preparing spirits for their mortality. This could be considered giving spirits their "first lessons", eternal parenting, or teaching "morality prep'.

There are 3 lessons that must be learned during mortality and can only be learned now. 1. love God 2. control the body 3. submit to God's priesthood authority. 

If you never learn these lessons here and now, you can never learn them and consequently, you can never teach what you have never learned. 

In my view, the 3 degrees of heaven are not physical separations but more of a division of responsibility. It's kinda like the hospital with techs, nurses, and doctors. We all work together, but there is a hierarchy of responsibility. God is the Great Physician, The Physician of physicians, who desires all His children to become doctors, but some will settle to be nurses and techs-- worlds without end. 

If you desire to become like, and do the work of our Heavenly Father, the time to decide is now. There is no going back to medical school later.