I learned about this word today too. It stands for 'Joy Of Missing Out".
You were thinking of buying a coin and later that coin dumps to oblivion. That's JOMO!
I feel very JOMO because it never touched at all DeFi when it was still very trending the same as NFT until now there has been none that I have and probably won't at all.
The defi and nft term are too general. Not all defi and nft projects are down and dumping but there are still few of them that manage to become successful now. I do not think you will feel jomo when you saw their positions now.
Investing when they are still starting can be beneficial because they are not in hype yet and there's only few people that invest on them but by the time they became too popular, more people then invest on and that should make their price pump but for now, the hype for defi and nft are slowly declining. I think investing on them is not really that recommended anymore. If you want to invest just go on the top coins.