The second most important thing is knowing that others enjoy and appreciate your efforts. That someone, somewhere likes the product of your work gives you a warm glow of satisfaction.
The first most important thing, however, is enjoying your work yourself. Push the papers and books aside, walk away from the conversations that fill the day, and spare a moment just to look at what you've done, nod to yourself, and smile.
I did that.
Clouds are soft enough to sneak up on ponies basking in your sun without being noticed. Just tossing that out there.