Humorist Mark Twain got it right when he said, “The most successful people are those who do all year long what they would otherwise do on their summer vacation.” Those are successful and happy people. You can build a career around virtually any subject, industry, or activity that you find interesting. Pick a career that corresponds to your interests, and just like the prolific inventor Thomas Edison, you may find it's so much fun that you'll never have to do a day's work in your life.