Fear and greed tend to affect one's judgement.
You have to have confidence in what you're doing.
Have a philosophy of investment and try to follow it.
Some kinds of stocks are easier to analyse than others.
My first job at Graham-Newman was to prepare the annual report for that 10th year.
If you are honest, hardworking, reasonably intelligent and have good common sense, you can do well in the investment field as long as you are not too greedy and don't get too emotional when things go against you.