Alright, you can try to teach yourself. You will fail, but you can try.
Let's say you are training alone. If you do a move and you think it looks right, you practice it and go on. However, what you don't realize is that you are rolling your back foot whenever you take a step forward and will destroy your ankle in a few months. Or, you could be hesitating on your strokes or leaving your left side open to attack the whole time.
These are all very common mistakes, and without a teacher, they will probably not be caught, and therefore, will never be corrected.
You might be able to learn from a book, and if you have no other option, you can find some around, but I would highly suggest that you do not.