When asked, many teachers would define success as a great lesson where students were engaged, on task, and learned the content. A great lesson is definitely a success, but it's also important for us, as educators, to celebrate all of our successes, not just the great lessons. The days we see our students solving a problem on their own instead of "tattling", when we see students collaborating to read and make sense of a poem..without being asked, a student purchasing another student a book at the book fair because they didn't bring any money - and not bragging about the fact that they did it, a student tying another's shoe because he can't bend down after surgery, a student standing in line- still working on the activity that they were supposed to stop because they are enjoying it so much, that "light-bulb".
As educators, it's so easy for us to be hard on ourselves and look at all the bad...because we are always expected to be better. But I want to encourage you to sit back at the end of the day and say, "What went well today?" and be proud of all those little (or big) accomplishments.