FOMO is just marketing that learned your name.

The feeling of missing out is manufactured with some precision. Scarcity, timing and the sight of other people already inside are all deliberate, and the sensation arrives before any thought about whether you wanted the thing. Recognising the mechanism does not switch the feeling off, and it does change what you do next.

When the urgency hits, put a gap between the feeling and the action. An hour, a day. Then ask whether you wanted this before you saw it. Often the answer is no and the feeling fades without argument. Occasionally it is yes, and now you are choosing rather than reacting.