"When I do good,I feel good. When I do bad I feel bad."
This quote means that you must do good thing in order to feel good. Like lets suppose you took a test and you got an "A" you're going to feel good because you  did good on the test. Another example is when you finish your homework you feel good but when you don't do it you're just so worry that your grade gets low.So you must always do good things inoder to feel good. And when you do bad you feel bad like when you don't do your homework you feel bad cause it can damage your grade.