Here's the "feel good" version:
I have been teaching physics at Holland High School for 15 years. I teach physics because I'm fascinated by this amazing universe in which we all find ourselves. Through the eyes of students, my excitement of discovery is continually renewed. When I teach, a small part of my enthusiasm for what I teach is instilled in the souls of my students. A portion of my hopes and dreams go with them when they leave my classroom. Though I may never move far from this place and time, their memories of our time together and the joy we experienced as we contemplated some of the deep mysteries (yes, these young people are capable of incredible insight) will travel with them the rest of their lives. Through them, some small part of me will continue on to places and times about which I can only dream.

For those of you not so "touchy-feely" here's version B:
I've been teaching physics at Holland High School for 15 years. I teach because I love young people, I love physics, and I love a challenge.