An unease that comes from feeling that one is disregarding or overlooking an advantageous opportunity or situation.
The fear of missing out (FOMO) is the unease that comes from thinking that you are losing out on an opportunity because of ignorance of said opportunity or doubts regarding its validity. Thus, the envisioned opportunity may or may not exist, but the human mind holds on to the suspicion that inactivity is going to lead to regrets later on. The implications of FOMO is that one contemplates making a decision based on this unease, and the decision often leads to disastrous implications.
In all kinds of trading, FOMO is one of the biggest indicators of an emotional trader and investor. This becomes more apparent when such individuals focus on the fluctuation of asset prices rather than the big picture of trading. Many traders who FOMO into an asset end up regretting it when the price then moves rapidly in the opposite direction.