Everything that Christianity says you should do, is under pain of damnation (or has no penalty at all). It's not as if God has some other punishment short of damnation that he administers instead when your sin is mild.

There are plenty of punishments short of eternal damnation that an omnipotent being can hand out.

From here:

Yet certain temporal consequences of sin remain in the baptized, such as suffering, illness, death, and such frailties inherent in life as weaknesses of character, and so on, as well as an inclination to sin that Tradition calls concupiscence, or metaphorically, "the tinder for sin" (fomes peccati);