Glory
There's a reason people get into education—it feels good to help students achieve.
Teachers want to share their love of learning, and they want students to build the skills they'll need to thrive later in life. If you're just looking to make a quick buck, there are plenty of other part-time jobs—if you're considering subbing, you have an interest in developing and educating young minds.
If it goes smoothly, subbing can be a rewarding experience. You meet kids for a day, spend a bit of time going over whatever materials they're working on, assist a few of them, and if you manage to pull off a lesson that gets them engaged, it can give you a little thrill of victory.
On the other hand, the day could go horribly, and then you end up wondering why in the world you'd ever subject yourself to this torture. The glory you get out of that will most likely be at the bottom of a pint of ice cream.
Try to let the bad days wash off your back, and hope for the good days to come again. It's always going to be a mixed bag—especially on the days they make you sub for math. No one's ever happy in those classes.