I have said FOMO is the worst of traders' emotions.
It's pretty simple.
Fear prevents you from taking positions. While fear can take a toll in opportunity cost, at least you keep your money.
But, FOMO causes you to take high prices in 'fear' of losing opportunity cost causing you to accept poor risk to reward.
FOMO is more pronounced in new or immature traders. Such traders trade each position as if its the last trade they'll ever find. That's simply a lack of confidence. As you gain mileage as a trader, you know there's another trader around the corner. If you're a scalper you know there is a trade every day.
Fortunately FOMO has a couple treatments:
1. Hold a core position in a bull market- What level are you comfortable holding through thick and thin until a level is breached that threatens a protracted downtrend?
2. When you take profit in a bull market, leave some on, maybe just your principle. Then, in turn, should your holding run, learn to accept the profit on a reduced position size. Take the cash and stalk a new trade.
3. Remind yourself that tomorrow may present another trade. Cash is a position, which is to say it is the power to take a new opportunity the market provides. You can't take that new opportunity if your cash is wrapped up in a trade that FOMO pushed you into at a bad price.