2 Nephi 2:11
11 For it must needs be, that there is an opposition in all things. If not so, my first-born in the wilderness, righteousness could not be brought to pass, neither wickedness, neither holiness nor misery, neither good nor bad. Wherefore, all things must needs be a compound in one...
I have long wondered about statements to the effect that we must not procrastinate the day of our repentance:
Alma 34:33
33 And now, as I said unto you before, as ye have had so many witnesses, therefore, I beseech of you that ye do not procrastinate the day of your repentance until the end; for after this day of life, which is given us to prepare for eternity, behold, if we do not improve our time while in this life, then cometh the night of darkness wherein there can be no labor performed.
A few subsequent thoughts on these ideas:
It is in mortality that we feel most acutely the tugs and pulls of opposing choices laid before us. In order to atone for us and truly come to know our burdens Jesus had to experience our burdens just as we do: in mortality!
Perhaps one reason it is so important to choose the right and repent while in mortality is because in this state our choices are laden with a high degree of opposition (and therefore opportunity). The stakes probably can't be as high for us in the spirit world because we lack a physical body to amplify the opposition and opportunity presented to us.
Also, as mortal beings we have the opportunity each week to partake of the sacrament, providing a very physical reminder of and connection to the Savior's atoning and healing power. I don't know how things are in the spirit world. I assume that those in that condition have the opportunity to worship God. It wouldn't surprise me if there are ordinances available to those in the spirit world which, like the sacrament, serve as reminders of the Savior's atoning sacrifice and a renewal of covenants (but I don't know that).
The ordinance of the Sacrament, however, strikes me as a very mortal experience, which requires eating and drinking, just as Jesus instituted. Perhaps not partaking of the sacrament is what makes repentance much more challenging in the spirit world.(?) We don't get the same kind of physical reminder of our covenants and the promised blessings. We are left to rely more on our memory of physical experiences.
Doctrine and Covenants 130:18-19
18 Whatever principle of intelligence we attain unto in this life, it will rise with us...
19 And if a person gains more knowledge and intelligence in this life through his diligence and obedience than another, he will have so much the advantage in the world to come.