Our joy cannot become full...until we see God's name fully hallowed, all false doctrines and sects extirpated, all tyrants and persecutors of His kingdom suppressed, all the godless, and the will and schemes of the devil checked, and God's will alone done; until the cares of life, our hunger and thirst, no longer assail us, no sin any longer oppresses us, no temptation any longer wearies the heart, and no death any longer holds us captive. But these things will happen in yonder life; there our cup will be full of joy and not a drop of sorrow will be in it any more. But in this life, as St. Paul says (I Cor. 13:12), things are done only in part, and we have only a drop of this joy by faith; this is the beginning or foretaste and sample, which grasps the comfort that Christ has redeemed us and that we have come into God's kingdom through Him... But we always fall into the mire again and become burdened with sadness and a heavy conscience, so that our joy cannot be pure or is actually so weak that we are scarcely able to feel even this beginning of it.
(What Luther Says - p. 691 - para 2144)