Catholic teaching is this: Man (basically Adam and Eve) was created good, that is, perfect in the human sense, without sin or flaw. Our first parents, as a total unmerited gift from God, were also given what are called
preternatural gifts, that is, they had perfect control over their appetites and passions, had infused knowledge of everything they needed or wanted to know, and were not subject to illness or natural death (presumably, they could have been injured or been killed, but in Paradise they were kept from that). Had they not sinned, when they had reached the end of their earthly lives, God would have taken them to heaven, body and soul (sound like someone we know?).
These preternatural gifts, as was mentioned, were gifts from God. Even though they had all these gifts, they still had free will, the misuse of which was how they sinned and fell. When they fell, they (and we) not only lost sanctifying grace (or, in Christian terms, justification), we all lost these preternatural gifts. Original sin, which is usually thought of something inflicted on us, is actually a lack of these graces which God added on to our natural state.
When we receive baptism in faith, we are restored to sanctifying grace, but we do not recieve the preternatural gifts. We can develop them as virtues when we are given graces by God (through the sacraments, for example), but it is a struggle. The struggle comes from what is called
concupisence (similar to what Protestants call the sin nature), sort of a scar left over from our fallen nature that fights against our good intentions. Temptations from the outside of us add to the difficulty, but primarily it is concupisence we struggle against, and with St. Paul we lament:“The good I want to do, I do not do, and the evil I do not want to do, I do.”
So to answer your question, the nature of man was created good; it is fallen, but through Christ is restored through faith, baptism, and obedience to the end. We fight against concupisence, but God in his mercy will give us all the grace we need to overcome, just for the asking.
Hope that helps.
