I think the overall theme of the movie would be to seize the day, and do what makes you happy. Mr. Keating told them that the first day, and he taught them how to do so throughout the whole story. They all seemed to seize the day one point or another. Todd seized the day on the day that Mr. Keating got fired and stood on top of that desk because its what he believed. Neil Seized the day the day he decided to stop listening to his dad and doing what he wanted most, to act. Also Knox, he probably seized the day the most, he was daring, didn't want to be like anyone else, he was brave. They all seized the day by standing by Mr. Keating the whole story, also by being a part of the dead poets society. Mr. Keating said that they were all gonna die one day so you might as well seize the moment and be you.