Is sanctification difficult?

Luther:

On one hand for sure, on the other hand not. For sure, because the old Adam in us does not want to die. But also not, because all things work together for good. As long as you are not governed by sin, sin is forced to serve you, as stands written in Romans 8:28: “All things work together for good to them that love God”. If you are attacked by lust, you finally become more chaste, by pride more humble, by idleness more diligent, by avarice more generous, by a spurt of anger more mild, by profusion more sober. Because the spiritual person becomes more and more angry that he is fallen in sin and he more and more opposes it. Therefore temptation is very helpful.