Laura Klein – Pain Driven Design:

"You see, no matter how much you love your product, unless it’s perfect, it’s causing pain to somebody. I’m sure it’s not on purpose. You’re not a monster. But something about your product is confusing or hard to use, and it’s driving at least one of your customers nuts.

Again, examine them. Find out when they feel the most pain while using your product. Watch brand new people use your product to see how much pain it takes to learn. Watch old customers use your product to figure out what weird workarounds they've created to avoid the pain that you’re causing them.

Find all the pain points. Then come up with devastatingly clever ways to fix them."