IMO, I think that the burning need for passion is highly overrated. I know that such an attitude goes against the mainstream but sometimes we're told to set out looking for things that either don't exist or that are just mirages so that not finding them doesn't mean that there's something wrong with you, it just might mean that such things don't exist, or are almost impossible to find.
I think that to expect a pure emotion of passion to last a lifetime (or a career) and to get you through all of the difficulties you will face is not a realistic proposition for the majority of people. Alternatively, I personally focus on developing competence at whatever I do. Whenever I feel that something sucks in my life it's usually not the thing itself but my attitude towards it and my ability to do it that truly suck! Once I realize this I give a little sigh and then choose either to quit or to knuckle down and get on with developing my abilities and overall competence at that particular thing. When I do that I grow as a person and I get a lot of personal satisfaction. In the end it is curiosity and a playful attitude allied to some vigorous concentration that keeps me going - never passion.
If you're curious about alternative ways of viewing problems you can read this article:
Conventional vs. Contrarian
Take care,
Nick