This quote means that life is all about action. In order to have a life that feels meaningful, it requires effort and movement. It means that life is not static or stagnant, but that it is dynamic, always changing and evolving. To “keep moving” is to keep taking action and to keep trying new things. It is to keep growing and learning, and to face challenges and obstacles. To be “alive” is to be actively engaging in life, to keep pushing forward and to keep challenging yourself.