I too have a hard time narrowing my interests down to one thing. This causes problems in that it's hard to follow a single career and get really good at that one thing. On the other hand, since I easily switch from one interest to another, I am very flexible in my job and when one kind of work isn't needed, I just switch to another. The result is I don't get laid off because I am not needed.
What I find frustrating about this approach is that I am a jack of all trades and a master of none. I'm a pretty good photographer. I can write well if I apply myself. I have a good general knowledge of many aspects of computer graphics and can do a little bit of everything in the field. But I don't stand out as really exceptional in any of these areas. If I could simply narrow my interests and work hard at only one subject, I could probably become quite good. But I get bored or frustrated and I wander off to do something entirely different on a regular basis.
My guess is that this is just a deep part of our personalities and I don't have much hope that it can be changed. The best approach is to try to find a way to make this approach to different interests work for you. In my case, I work for a very small company that doesn't need a full time computer animator but has a use for someone who can do some computer animation, some photography, some photo retouching, some web design etc. I am sometimes criticized for not being as good as others in any particular field, but there are very few people who have the range of skills I have. I think that's how you have to promote yourself when looking for work. And you should think about how you can integrate your numerous interests into a kind of work that brings together different fields of study rather than becoming an expert at a single field.
And in answer to The_Perfect_Storm, here is the wikipedia definition
Quote:
An existential crisis is a stage of development at which an individual questions the very foundations of his or her life: whether his or her life has any meaning, purpose or value. This issue of the meaning and purpose of existence is the topic of the philosophical school of existentialism.
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Never let the weeds get higher than the garden,
Always keep a sapphire in your mind.
(Tom Waits "Get Behind the Mule")