Lest WE Be Castaways

But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway. 
1 Cor. 9:27

Castaway: Greek, Adokimos, ad-ok'-ee-mos
Adjective
Definition:
not standing the test, not approved
that which does not prove itself such as it ought
unfit for, unproved, spurious, reprobate



“Castaway” is used six times as “reprobate”…once as “castaway” in the KJV.

Adokimos: signifying "not standing the test, rejected" (prefix “a” = negative, “dokimos” = approved),
was primarily applied to metals *(cp. Isa. 1:22);
it is used always in the NT in a Passive sense…
(a) ...metaphorically, of things, Heb. 6:8, But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned.
"rejected"  of land that bears thorns and thistles…
(b) of persons, Rom. 1:28, And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient
...of a "reprobate mind," a mind of which God cannot approve, and which must be rejected by Him
…the effect of refusing "to have God in their knowledge"…
2 Cor. 13:5...Examine yourselves, whether you be in the faith; prove your own selves. Know you not your own selves, how that Jesus Christ is in you, except you be reprobates?
 here the reference is to the great test as to whether Christ is in a person…
in 2 Tim. 3:8... Now as Jannes and Jambres withstood Moses, so do these also resist the truth: men of corrupt minds, reprobate concerning the faith.
...of those "reprobate concerning the faith," i.e., men whose moral sense is perverted and whose minds are beclouded with their own speculations…
in Titus 1:16... Such people claim they know God, but they deny him by the way they live. They are detestable and disobedient, worthless for doing anything good.
...of the defiled, who are "unto every good work reprobate," i.e., if they are put to the test in regard to any good work (in contrast to their profession), they can only be rejected…

In the Septuagint… Proverbs 25:4:
Take away the dross from silver,
And it will go to the silversmith for jewelry.
Take away the wicked from before the king,
And his throne will be established in righteousness…

*…in Isaiah 1:22:
Your silver has become dross,
Your wine mixed with water.

Most other Bible translations use the word “disqualified” such as, for service.
At best, the reference is to “useless, or worthless.” But, I believe, it could also indicate an enemy of God, willfully or unconsciously, because "useless" in the spiritual sense is very serious. It puts one at odds with God's Will and Purpose.
I read it as the opposite of…
“Well done good and faithful servant.” Matthew 25:23.

Let us put ourselves to that great test and examine ourselves.