When it's said and done, the one thing I want to leave on this earth is hope. I have felt hopelessness, and it's a terrible feeling. Hopelessness will destroy you. I want to bring hope to other people.

This quote means that when the person is done living their life, the one thing they want to bring to the world is hope. They understand what it feels like to be without hope and how damaging it is. They want to help other people by giving them hope and making sure they don’t feel the same way.