The true evangelical use of the Scriptural doctrine on the reward of good works

First, it is important to note that Franz Pieper gives "the reward of good works" its own heading and treats "the great worth of good works" seperately (Bd. III, pg 64ff.) These doctrines are responses to two different errors, and they drive different preachments. Both contain admonition, but the former is particularly consoling. And this is its use, to console those who suffer and to encourage those who are weak or wish to look back once having put the hand to the plow.

Pieper concludes "the reward of good works" with a lengthy Luther quote, in which Luther takes on the subject in the Bergpredigt and Matthew's Gospel as a whole. Luther, interestingly, is reluctant to broach the subject, but admits that he can't ignore it since it comes up so frequently in Scripture. It raises a sharp question that belongs more to the schools of the learned than to the pulpit before the simple. He says that one must first distinguish between grace and reward. Where one speaks of grace one may not speak of reward and vice-versa, but the real distinction here is between grace as unmerited favor, justification, eternal life, heaven, and all other gifts, which while given nevertheless correspond to that which one is given to do, such as suffer with sin.
The world tightens around you because your flesh, the devil, and the world hang on you. In the face of this we might despair and say, "Who wants to be a Christian, preach, and do good works?" Well, God has promised you rewards in this life and the life to come. It's his promise that matters here and not the "worth" of your works. The "worth" of works has to do with the neighbor. This is Gospel, however, that God has promised rewards here and in the age to come. Everything banks on this. There's comfort in the promise. The works themselves are still stained with sin (a point that Pieper is quick to make). Don't look to them but to the promise. It's the promise and not your works that you hold before God. Endure the suffering. Do what you are given to do.