If we're talking web design, the answer is everything. Don't believe me? Ask Kathy Sierra. She'll tell you there's one way to be successful on the web—create passionate users. And the only way to do that is to be passionate yourself. I don't have stats on this (although Sierra probably does), but I have enough experience to know it's true. I quit professional writing because it had stopped delighting me. That may sound like a lame excuse to chuck a viable writing career, until you imagine trying to write a scene in which two people you don't care about fall in love. I kept wanting to play with HTML instead of working on chapter 9. Needless to say, my last manuscript stank (and, luckily for readers, was never published). An author friend of mine, who is still publishing, once said to me, "If you don't love it with all your heart, if you don't want to be published more than anything in the world, get out. This business is so tough, you'll never survive it if you aren't driven." I think the same thing translates to web design...and maybe most professions. Yes, you can be a drudge, churning out page after page of CSS code and watching the clock. But that's not what we're talking about here. To be an excellent web designer, you must be passionate—passion breeds excellence. When you are passionate about and excel at what you do, your job stops being your job and becomes your joy. Just think what it takes to master this professional. You need to know CSS and HTML like it's your native language; be skilled in graphic design; possess an understanding of accessibility, usability, information architecture, marketing and SEO; and have enough familiarity with languages like PHP and Javascript to work with web applications like content management systems. And because it's the web—and alive and changing everyday—you can never stop studying it, but must always be ready to turn on a dime and take up anything new that comes along. To accomplish all that takes drive and the will to excel. It takes passion. What's love got to do with it? Everything, my friend. Everything.