I think that there are some jobs that if you actively want to do them, you probably shouldn't be allowed to do.
Politician could be one; policing is perhaps another.
I'm not implying that everyone that wants to do these jobs is inherently deranged in some way. I was merely daydreaming idly and it occurred to me that, if you quite like the idea of beating people up and handcuffing them and putting them in prison or something, could it be that being a policeman is a dangerous move for you and for society? Or, if you like the idea of having your finger on the buttons that control society, perhaps you should keep your sticky mitts to yourself. Maybe the best kinds of leaders are reluctant and accidental ones: at least then they are motivated in an appropriate way...
I propose that in order to address this problem, we should have some kind of conscription that dictates we all must do a year or two as policemen and politicians, whether we want to or not. Yeah, there'd be some pretty poor policing and idiotically incompetent politicking going on, but at least it would be well intentioned.
It's just that I was bought up to believe that it's the thought that counts.