Most of the important things in the world have been accomplished by people who have kept on trying when there seemed to be no hope at all.

This quote is saying that a lot of the most meaningful achievements in the world have been made by people who kept on trying, even when it seemed like there was no hope of succeeding. It is encouraging people not to give up, even if success appears to be impossible. It is telling us that, with enough determination and perseverance, seemingly impossible goals can eventually be reached.