What is lacking? Colossians 1:24

I don't know about you guys, but I read God's word and accept it as the truth, but sometimes, I have no idea what something means! This year, I have been reading a lot of Colossians, and I love it, but one verse that trips me up:

Colossians 1:24
²⁴Now I rejoice in what was suffered for you, and I fill up in my flesh what is still lacking in regard to Christ's afflictions, for the sake of his body, which is the church. (NIV)

*And KJV, for good measure:
²⁴Who now rejoice in my sufferings for you, and fill up that which is behind of the afflictions of Christ in my flesh for his body's sake, which is the church:

Now, what is lacking? I certainly don't think that Christ's sacrifice was lacking in any way for my salvation, so then what does it mean? Well ta-da! Dr. Sam Storms wrote a little summary of some possibilities for this. Also, I believe John Piper is a wise man of God, so I liked that his commentary was present in the essay. It all makes a little more sense now...

"The fifth option has been defended by John Piper (Desiring God: Meditations of a Christian Hedonist, 2003). "Paul's sufferings," he explains, "complete Christ's afflictions not by adding anything to their worth, but by extending them to the people they were meant to save. What is lacking in the afflictions of Christ is not that they are deficient in worth, as though they could not sufficiently cover the sins of all who believe. What is lacking is that the infinite value of Christ's afflictions is not known and trusted in the world. . . . So the afflictions of Christ are 'lacking' in the sense that they are not seen and known and loved among the nations. They must be carried by the ministers of the Word. And those ministers of the Word 'complete' [or 'fill up'] what is lacking in the afflictions of Christ by extending them to others" (268).

What is lacking, then, in Christ's afflictions is not propitiation but presentation. In other words, the sufferings of Jesus fully satisfied the wrath of God, but there is lacking "a personal presentation by Christ Himself to the nations of the world. God's answer to this lack is to call the people of Christ (people like Paul) to make a personal presentation of the afflictions of Christ to the world. In doing this, we 'fill up what is lacking in Christ's afflictions.' We finish what they were designed for, a personal presentation to the people who do not know about their infinite worth" (269).

The amazing think about this text is how Paul envisions himself (and others) filling up this lack. It is in his "flesh"! In other words, "God intends for the afflictions of Christ to be presented to the world through the afflictions of His people. . . . Our calling is to make the afflictions of Christ real for people by the afflictions we experience in bringing them the message of salvation. Since Christ is no longer on the earth, He wants His body, the church, to reveal His suffering in its suffering" (269-70)."

(The entire article is here: http://www.enjoyinggodministries.com/article/filling-up-the-afflictions-of-christ-124/ ).