When you work with so tough challenging behaviour students in a high stander school environment then it is easy to feel down when you have been asked about the outcomes and its quality in so crowded day by many tasks and To Do List. The only question flows in your mind at night is how to survive on the next day!
Actually, your motivation should derive from your students. They are your strength when you already built the right relationship with cement of "love" and "respect". Trust them and believe in their abilities. Your students are not robots but humans who can feel your attitude and need to fulfill the curiosity of "why" questions. Actually, it is an almost universal law, their reaction depends on your action. Remember, they will pay back later but in different ways. It is a matter of time to harvest what you planted.
Whenever you are in a hard time, simply repeat it continuously in your heart: " But I love my children" because they are only who trust in you as their moral and example for their future.