see-saw of success

Success is an interesting concept.  I never could have imagined how much the definition of success would change according to those who gain it.  What is successful in one class may be failure in another.  I guess that's not such a foreign concept, just one that I have yet to experience, but encounter frequently now from the position I hold.  How do I tell if my assignments are successful?  How do I tell if my students are learning?  It just changes so much from class to class that I found myself running around in circles trying to figure out just this!  So, so far this is what I have got; success is a see-saw.  The harder I work to life my students the higher they fly, thus springing me to success on the other side as well.  Sounds pretty cut and dry, eh?  Not so much :(  But, at the very least, I can determine if a particular lesson was successful due to the assortment of frazzled look's on my students' faces.  At that point, I either do mental somersaults and backflips for joy or I run screaming into the streets.  It's a tossup!