What type of skill is hard to learn but pays off forever?

Developing a powerful memory can be achieved through systematic training and dedication, although it requires sustained effort. While it may not be necessary to memorize entire textbooks, enhancing memory skills can have significant advantages in analytical thinking and creativity. Analytical thinking relies on internal knowledge and details rather than relying solely on external access to information. Intellectual creativity is enhanced when one can observe complex patterns across various fields of knowledge. In conclusion, memory serves as the foundation for analytical and creative thinking, and developing this skill can greatly benefit individuals in various areas of life.