There is a subtle difference though. If people are greedy, but are about to get greedier, you need to be greedy, not fearful. You need to be greedier than they presently are.
Likewise for fear. If they are scared, but about to become even more scared, you don't want to become greedy. You want to get more scared than they presently are.
Basically, you want to be what they will be before they become it.
Gold investors are greedy right now. But that doesn't mean you should become fearful and try to sell or short gold. Investors are greedy, they see profits, everyone loves gold, but that frothy trend is perfectly intact, and is set to increase as more and more people catch the bug and decide they want out of paper and into metals that go up 3% on a down day. So anticipate the move and load up now.