I'm not prone to boredom but some divers I know are. The usual cure for this is taking more courses, diving deeper, in wrecks or caves, or trying sidemount or rebreathers...
We are blessed to be able to dive week in and week out and sometimes people get tired of doing the same old sites but aren't interested in those pursuits. I cured the blahs a couple of years ago by getting into videography. Now I don't care where I dive as long as there is some sort of subject to record. Even if the subject is mundane I work at different aspects of video, trying to develop camera angles and techniques.
For those who aren't into photo/videography, interest or cost wise, underwater drawing seems like a cheap, neat way to add a sense of purpose to your diving and a great way to work on buoyancy skills.