Dr. Stephen Krashen is a well-known educator in the United States who has published many books and articles about second-language learning.
Krashen distinguishes between learning a second language and acquiring it. Learning includes memorizing vocabulary and grammatical rules. Speaking or writing the language is hard work. Your mind is constantly monitoring your actions and correcting your efforts. When you write something, you have to go back and re-read it and correct the grammatical errors. When you speak, you say a phrase, and then immediately realize that you made an error, and then you repeat the phrase correctly.
Acquiring a second language (according to Krashen) is done by reading and listening to interesting and comprehensible material in the language. After you have read and listened enough, you can speak and write the language without thinking about the vocabulary or rules. This is the way children learn to speak a language (or two or three) before they start school.
The two key concepts in acquiring a language are “interesting” and “comprehensible”. If the reading or listening material is not interesting, you will not pay attention. If the material is too difficult to be understood at all, you won’t acquire anything.
As an adult student of Esperanto, you can acquire the language while you are learning it. The trick is to find interesting reading and listening materials and enjoy them. The amount of reading material for beginners is limited, and the amount of listening material for beginners is even more limited, but you can find some in various Internet sites and specifically at the Esperanto-USA online store.