I've noticed that when people need to learn a new subject for school or work, or because they just want to, they approach the task with fear and are sometimes so intimidated that they chicken-out and return to the comfort of what they already know. This is a pity because knowledge of any subject--be it math, science, history, art, cooking or others--is made out of the same stuff as the subjects they've already become expert in, and all knowledge is enriching no matter what the subject is.
To help ease one's submersion into a new subject, a few mental tricks can be applied. The first is to assume you already know something about it and are just out to make your knowledge a little bit more complete every day. Your attitude should be humble confidence: you know you can know, but you need to beef-up what you know before you begin talking about the subject with authority.
This assumption is philosophically valid because all domains of knowledge overlap each other, and what we call a "subject" is knowledge that's simply more specific and better qualified.
When you "assume you already know" you can jump into a new subject at the deep end and learn in branches: if you pick up a book on your new subject and read a word or term that you don't understand, pause and look-up what it means. When reading the definition you may come across yet another term that's new to you, and so you'll pause and begin another branch of research. Do this in a web browser and open a new tab for each branch, and after a while you'll be able to close branches that you've exhausted and even come full circle back to where you started.
Don't be surprised if it takes you a few hours or days to get through the first paragraph of a book or magazine article that's rich in the special vocabulary of the new subject. Take your time and don't be afraid to split off on as many branches as you need.