Lukeprog at Less Wrong talks about what he learned about interpersonal communication in a Scientology class, and what it taught him about learning:
Building small skills in the right order is an excellent way to create and maintain success spirals.
Trying to master a large skill set like salesmanship is a daunting task that will likely involve many demotivating failures before you ever taste success. The same goes for public speaking, writing research papers, and lots of other large skill sets involving a complex interaction of many small skills.
Anna Salamon uses math to explain this concept. You could tackle calculus immediately after Algebra I, and you might eventually pick it up after many frustrating failures if you read the calculus textbook enough times, but why would you do this? It’s much easier and more satisfying to learn more algebra piece by piece until the jump to calculus is not so great. That way, you can experience the pleasure and confidence-boost of mastering new concepts all along the way to calculus.