You know what "For Adults Only" means. X-rated. Porn star. "Explicit material." Seedy characters walking into an adult video store just off the Interstate. The word "adult" is commonly used this way.
So what does it mean to be an adult?
Some stuff that you can complain about all day (both about yourself and about others) without being called a Jesus freak. This stuff applies to everyone, regardless of your vocabulary blacklist.