"Many commit the same crime with a very different result. One bears a cross for his crime; another a crown."
Juvenal observes the seemingly random play of fate in people's lives. There are few, if any, actions which have never been performed before, so every time a person makes a decision they are invoking fate whether they will succeed or fail. In Juvenal's opinion, this process is entirely random.
"Many suffer from the incurable disease of writing, and it becomes chronic in their sick minds."
In this quotation, Juvenal reveals something about his own relationship to writing. Viewing the process as an incurable disease, he describes how he writes compulsively. The writing, however, bring him no satisfaction or blessing; rather, he appears to have an antagonistic relationship with writing.
"No man becomes bad all at once."
This is a famous maxim of Juvenal's. He is explaining that the summation of a person's decisions build and eventually form that person's character. One lone choice, however, cannot make a person bad. Additionally, in order to corrupt one's character one must remain distant and uncorrected continually by other people, so there is also present in this quote an implication of the responsibility of society or community in the ethics of its citizens.
"It is to be prayed that the mind be sound in a sound body.
Ask for a brave soul that lacks the fear of death,
which places the length of life last among nature's blessings,
which is able to bear whatever kind of sufferings. . ."
Juvenal appears to think more highly of how one approaches death than how one approaches life itself. He admires the person who does not fear death because they have valued life appropriately and lived it already to its fullest. He urges the reader to ask for deliverance from the fear of death in order to be united body and mind in the accomplishment of one's will.