you know job interviewers do not like this. I am shit at selling anything, that includes myself, and most of employers sarcastically ask - but how can I be sure that you will be a good worker? According to you previous experience, you may not show up for the work, because you decided to hitchhike to Bulgaria, photographing birds at some stranger's farm. Being passionate about most of the things has its negative side.
I've both been the interviewer and the one being interviewed. I can say that without a doubt the #1 thing I look for in someone is passion. When I ask someone about their past work experiences I want to hear passion in their recollection, not regret or bitterness. When I ask them to tell me about themselves etc, I want to hear passion. Apathy sucks. Passion is where it's at. I've never left an interview thinking "man, I think I may have come across as too passionate."
I think tng refers to finding passion in his work, not being a creature so moved by passing fancies and whims that he will randomly hitchhike to Bulgaria. The only downsides I can see about being passionate is: 1) you scare off people who aren't passionate 2) you have an emotional investment in what you're doing and so can experience emotional hurt if things don't go well