I am not sure that a person can decide not to be, say, a kleptomaniac or voyeur, nor does it seem possible to decide to be one.  Such things may be innate, characterological, or at least determined before one reaches the age at which one imagines oneself able to make such decisions.  If such decisions can be made — and not only made but effected — then I would say that one of the chief reasons not to be, for example, a kleptomaniac is that it will lead you to worry about other people stealing from you.  Similarly, the voyeur will worry about Peeping Toms and Marys, a gossip about gossip.

          Of course life might otherwise teach you to worry about thieves, voyeurs or malicious gossips.  And it seems reasonable to assume that in a given situation — in his office — a voyeur or snoop could refrain from such behavior and thus feel less vulnerable to colleagues' curiosity.

          Now the matter becomes more complex, however, because in my experience, it is better not to trust other people until they have proven themselves trustworthy, rather than to begin by trusting people and be deceived and disillusioned time and again.  Shall we then conclude that the malicious gossip, because of his fear of what other people might say about him, begins a job not only better armed but also better prepared to be pleasantly surprised than someone of a more laudable character?

          Similarly, La Rochefoucauld noted that the best defense against flattery is an excessively high opinion of oneself.