[omgJustTest]

I agree with the above. Additionally: know what you are buying and know the rules.

For example, a less sophisticated instrument is a stock. Why does a stock have value? What do you get in exchange for money? Why are companies incentivized to care about stock prices? Why are stable companies often devalued if they have less growth potential?

These seem like basic questions, but if you think about any one of these they are not easy to answer.