This is the third time I've been staring blankly at the mempool in congestion... You think clicking send is the end of it, but actually you're just joining the queue: others are paying more to cut in line, your transaction gets moved back and forth, and if the gas fee is too low, it stays "unconfirmed" forever. What's more annoying is seeing a bunch of replace/cancel transactions from the same address ahead, indicating someone is repeatedly adjusting the price to probe. The easiest pitfalls are slippage and timing—waiting too long means the price has changed, resulting in either a failed transaction with wasted gas or a fill at a price you don't want. Honestly, there's a sense of "fake liquidity" on the chain too, hanging around to make you think it can go through, but when congestion hits, everything gets canceled. Recently, the yield stacking from staking has been criticized as "nested," but I think it's similar: layer after layer gets added, and when the critical moment comes and the queue gets blocked, adjusting the priority immediately reveals who runs first and who stays behind. Anyway, I now prefer to do fewer transactions rather than get stuck at the end of the line and lose my patience.