If we are Christians, we have understood and acted upon the finished work of Christ once and for all at our justification, and our guilt is gone forever. Now let us understand and act upon the practice of that same work moment by moment in our present lives.
Let me repeat: the only difference in the practice is that in justification it is once for all, and the Christian life is lived moment by moment. The Christian life is acting moment by moment on the same principle, and in the same way, as I acted at the moment of my justification.
But let us notice that from another perspective, even at this point it is not really different, because life is only a succession of moments, one moment at a time. When we say 'moment by moment,' we are dealing in practice with a succession of single, historical moments. No one lives his whole life at a time. This is another of these places where the existentialists have made a very accurate observation. Life is not a once-for-all thing; it is a series of moments. So when I talk about living the Christian life moment by moment, I can only live it in practice one moment at a time, just as my justification took place in one moment. There is no other way to do it. In this sense, the difference is not absolute between the two. Nobody can live except moment by moment, and only one moment at a time. . . .
So we must believe God's promises at this one moment in which we are. Consequently, in believing God's promises, we apply them--the present meaning of the work of Christ for the Christian--for and in this one moment. If you only can see that, everything changes. As we believe God for this moment, the Holy Spirit is not quenched. And through his agency, the risen and glorified Christ, as the Bridegroom of the bride, the Vine, brings forth his fruit through us at this moment.
This is the practice of active passivity. And it is the only way anybody can live; there is no other way to live but moment by moment.--Francis Schaeffer, True Spirituality (Tyndale House, 2011), 77; italics original
Conclusion: I do not have to live an entire life's worth of Christian obedience and risk and self-denial today. I am called simply to let today unfold, taking God at his word moment by moment, receiving the gospel down into my soul hundreds of times today, hitting refresh time and again. Each day has enough trouble of its own.