When I think about it, the happiest and most successful people I know don't just love what they do, they're obsessed with solving something that matters to them. They remind me of a dog chasing a tennis ball: Their eyes go a little crazy, the leash snaps and they go bounding off, plowing through whatever gets in the way.

I think people live in the past and tend to look that way, because they drop off when they're happiest and most successful.

Remind yourself regularly that you are better than you think you are. Successful people are not superhuman. Success does not require a super-intellect. Nor is there anything mystical about success. And success doesn't based on luck. Successful people are just ordinary folks who have developed belief in themselves and what they do. Never -- yes, never -- sell yourself short.

The most successful people are so original.

I think I'm probably a little too desperate to be successful.

You think about who needs Dropbox, and it's just about anybody with a pulse.