Focus on several areas
This has been argued for a very long time: what is better - to study different areas or to focus on some one. In defense of the first opinion, we can say only one thing: look at Ilona Mask. Many successful people achieve great results because they are educated and are curious in many areas.
Consider everything as an opportunity to learn
Do not think that you learn when you read books or solve mathematical problems. Everything that happens around is an excuse to learn something new.
While traditional education treats learning as attending school and university, doing homework, self-study requires much more.
Use the best online resources
There can be no justification for the lack of opportunities: today there are thousands of free courses available for almost anything. Of course, they will not make you an expert, but a basic understanding of the chosen subject matter will be given. And to study at Harvard, you do not even need to leave the house.
Meticulous look for the right books
Self-learning is great, which allows you to decide what you will study. It, the truth, puts before a choice: and what, actually, to read? At first, you are likely to make a lot of mistakes and buy unnecessary books. But with experience will come an intuitive and rational understanding.