John Spencer writes a blog that serves as one of my absolute favorite places on the Internet to find a good read. He's thoughtful, insightful, humble, honest. Start at the beginning and read the whole thing.
But if you're in a hurry, and especially if you're heading into your first year of teaching, read John's warm and encouraging letter to himself as a first year teacher:
A Note To Myself As A First-Year Teacher (Education ReThink)