Since they have suffered, the writer encourages his readers not to throw away what they have done thus far. Compared to their suffering, their reward is great! To continue the athletic metaphor, only the one who competes to the end of the race wins the prize. There is no “participation” award for those who quit the race early.
The readers have “great confidence.” This is the same word he used in the previous section to describe our access to the Throne of God. If that is the level of confidence we have there is every reason to believe that we will overcome whatever suffering we may presently face.
Therefore, the readers ought not “shrink back and are destroyed.” The noun ὑποστολή only appears here in the New Testament and has the idea of being timid, shy, hesitant. This is the opposite of the confidence which we have before God. According to the argument of Hebrews, the salvation we have in Jesus is so great that we can “boldly enter the throne room of grace.” Imagine the boldness it would take to enter into the Holy of Holies in order to worship God!
If we have confidence before the throne of almighty God, why are we timid in a public trial? Why are we so timid even when we are not in a public trial?