moved here from the craziest bastards on earth
We're all a little worried that we're insane. If we weren't then we might actually *be* insane, well most of us, anyway. The point is although we recognize faults in our own reasoning, we seldom if ever do anything to fix these unless we regard them as being serious. In most cases the problems are transitory: depression, anxiety, hallucinations, they all pass. We have to accept this because most of us don't study what these things actually are, and how and when to fix them.
You're average Psych person is in a different position. The object of their curiosity is the human mind, and it's flaws are the substance of their own analytical tendencies. This would be fine if one had a perfect mind, and only saw such flaws in others, but when you begin to see them in yourself, it has an unnerving effect. Not least because you know in most cases what the worst case scenario could be. Psychiatrists are actively discouraged from self medication, and it undermines one's reputation as a Psych professional to seek advice from others in the field, especially when you regard them as being less experienced than you. How many computer scientists would pay Microsoft Support £2 a minute to talk them through a reboot if WinXP crashed? Not many I daresay. However in the mental realm this pride and personal assessment of other's ability to help plays a big part in the growth of mental problems.
If you combine this with the eventual realization that the problem may have grown out of their control, you can imagine the impact this would have on their ability to function.
For the record I don't think Psychiatrists and Psychologists are more crazy than the rest of us, I think they just as crazy, but they either have to cope with their issues exceptionally well, or hide them even better. Sometimes the pressure of doing so on a daily basis can lead to the tragic consequences that Dannye described. Even a shrink needs someone to lean on, sometimes.