Reading quietly on the subway on the way downtown.
Getting to class a little later than usual (but still before it starts) and having people worried about you.
Having a great class, where the students pull some amazing stuff off, impressing the hell out of you.
Having them thank you at the end of the last class.
Having a few tell you "You're the reason I kept coming back. You made it fun."
Stopping at Harvard square on the way home and watching the people.
Finding what you need in Harvard Square.
Stopping by a mailbox on the drive from the subway station to mail a letter.
Making room so that a little old lady can park behind you.
Dropping your letter in the mailbox, and looking up to see the little old lady smiling at you from her driver's seat.
Walking over to her car, opening the door, taking the letter she's waving and putting it the mailbox for her.
Hearing a simple "Thank you."