It is hard to be happy with what you are doing if you are comparing yourself to others or against an entire field of knowledge.

It is necessary to be more specific about what you want to learn. Wanting to learn about "astrophysics" is too general/broad. You have to "drill down" to something practical that you can hold on to: Kepler, Kepler's first law (law of ellipses), down to ellipses and how they work, as related to astrophysics, or math, or English, but not all three (or all three if that is what you want to learn)! It takes wanting to focus and practicing discipline to bring yourself back from "Oh, look, they have ellipses in English, too!"

You can never get ahead of everybody because everybody is on their own schedule and started sooner/later than you did or are faster/slower learners than you are or more/less concentrated in whatever subject you are studying. Maybe you become knowledgeable about Kepler, but someone else wanted to focus on the Doppler effect or Newton's Laws of Motion. You cannot learn "everything" or be ahead of "everybody" and trying to do either will make you crazy (crazier? :-)

If I were you, I would take a single text/book you like (I know you are not in school but all subjects have basic text/books) and take the table of contents and a piece of paper and pencil and list the one-word or very short phrase subject of each chapter. I would then spend a week studying that word/idea 1-4 hours a day, however I liked. At the end of the week, I would read the chapter and compare it to what I had learned, what information was now "mine" because I had been concentrating on it for a week, and take notes on whatever else I wanted to know. If you are not in school, memorizing stuff in the traditional way (that doesn't work for you) does not make sense.

If you are studying a math, science, computer or other business subject, I would, after I'd read the chapter, do a few of the problems in the chapter/at the end. Presumably, if you are studying such a subject (like accounting), you will have come up with examples and problems as you studied it each day for the week. You might have set up your own system and be using it in your own home/work so be getting practice using it.

A lot of university professors have online pages to help their students; for example, I used this one http://www.physics.rutgers.edu/ugrad/341/ to look at what was involved in astrophysics and Kepler: http://www.physicsclassroom.com/class/circles/u6l4a.cfm.

If you are going to be going back to school and want to be "ahead" (know what courses you will be required to take) and more comfortable with the material before you are presented with it, I would look for college/university pages on the subject and work through them that way, staying with one syllabus/one text and single word subjects, "drilling down" as far as interests you and practicing staying focused (Kepler has three laws, you do each in turn, the 1st is about ellipses and you stay on how they relate to Kepler's law, not math in general or English). Usually such university pages are a bit limited in what they contain but that is good; it doesn't require notes or listening to lectures and will be easier to start with one word only and drill down, not going too far in sideway directions.