This is from my notes on finding the job of your dreams:
How to Select the job of Your Dreams
There are lots of guides that will tell you what future fields will be hot. Don't believe them.  Often they are wrong because managers tend to overestimate future needs. Schools want to attract students so they often exaggerate the demand for the professions they teach. Besides that,  no one can predict the future or the impact of technology.
The best thing you can do is pick a field that you have a passion for working in.  People are spending more and more time on the job, so doesn't it make sense that you should be doing something fun?
Surprisingly many of us don't know where our passion lies.  Also our interests can change from decade to decade and even from year to year.

Coming Next: How to create a job based on your interests.