The doubter would be urged to get busy doing good works. He simply wants to make it to heaven. If it takes good works, then he will likely do his best to produce those works. Ah, but there's the rub. Then justification really isn't by faith alone.
Justification is then by faith plus works.
While failure is sad, it is not proof that one is unsaved. I am not against God's commands. On the gospel I think I am in agreement with John Calvin, even though I don't believe that good works are a condition of eternal life. I know of no place in the Reformer's writings where he taught that good works were a condition of eternal life. However, even if it could be shown that this was Calvin's view, that would not move me, since ultimately I am indebted to God's Word, and not to a system of theology, for my view of the gospel.