Greed seems bad in everyone's view but you can't deny that thanks to greed, people are more likely to hold and push the price higher. You've to understand now all greed is bad since crypto has some form of greed in itself, attract investors thank to the 'get rich quick' scheme and exposing it to the mass public and social media.
Controlling greed is of course important in trading. Because traders who control greed get good results in trading. Because trading is a game of experience, any move in the hope of a quick profit can be costly.
The way everything is promoted on social media today about trading, things are shown to be very different from the reality. So a trader must follow the market trend and take trades after controlling greed.