1. A tree that old literally just exists motionless from day to day. A tree takes no conscious part in its own existence, similar to a person who is unmotivated and apathetic.
2. The reason is this: The oak tree has lived a long time, but the life has been empty and meaningless. The lily's life, though short, at least has aesthetic benefit.
3. The oak represents a person who feels it's sufficient to simply exist. Such a person is content to merely be born, live a long time, and die. On the other hand, the lily represents a life that is brief, yet full and satisfying.
4. People usually think something is special and important only if it's big and sensational, but the fact is, the most wonderful aspects of Life actually occur in small, short moments.
5. A person has truly lived when he has accomplished something meaningful with his life. A person who merely exists is someone who doesn't strive to achieve anything, improve himself, or make some sort of beneficial contribution to society.