I believe what St.Bernard says. I think the answer lies with St. Augustine. All men always look for the good.
Now, Augustine adds that the good is not always the right. A thief is looking for the good. He is thinking about what is good for him. He is not thinking about what is morally good, but a short-term good.
Add to that what Karl Rhaner says about man’s transcendental nature. Man has an innate drive toward the transcendant.
If Augustine and Rahner are right, a man (or woman) in grave sin will have a stronger drive to find his way out of a state that does not yield the happiness for which he seeks.
In the meantime, a person who is a good person, but who has room to grow, such as one who commits habitual venial sins and so forth, does not experience that strong drive toward the transcendant good, because (as Rhaner also says) man has an innate laziness and often settles for the middle. Man’s greatest fault is not grave sin, but his gravest sin is his failure to aspire to be better than mediocre.
I’ve always liked that thought. Neither Augustine’s nor Rhaner’s theses are taught as doctrines and they did not postulate them as such. They are interesting philosophical constructs that woud help explain what Bernard may have been thinking about.
Br. JR, OSF