To learn any language, including Lojban, you must lose your adult self-consciousness, and learn like a child. You'll learn much more quickly and will speak fluent and error-free Lojban within a few months. In learning Lojban, do not be afraid to make mistakes. You will learn from those mistakes, just as children do, and more quickly master Lojban. In addition, adults have more responsibilities than children, and find it more difficult to sustain long-term effort at learning.
Adults also have higher expectations of themselves, and get discouraged more easily.
A child does not expect total mastery of a language in a few months. After leaving formal school, most adults find it difficult to pursue even a single course of study for more than a few months. Recognize your limitations, but take pride in your progress. You will find yourself capable of expressing far more in Lojban in a very short time than you can in comparable effort in learning any other language.