Just while eating late-night snacks, I glanced at the mempool.

When there's congestion, your transaction is really like waiting in line to buy bubble tea:
first thrown into the pool to wait for miners/validators to pick,
if you pay a reasonable fee, you just wait patiently;
someone adds a higher fee to cut in line, and you move back...
you might even encounter the same transaction being replaced by a higher fee (some replacements fail),
anyway, watching pending transactions and zoning out can be pretty frustrating.
Honestly, it's not "once sent, it's done," but "once sent, the bidding begins."

Sometimes I’d rather cancel and redo,
rather than get stuck, especially with DeFi interactions,
when the price changes later or the pool gets eaten up by others,
being stuck means paying slippage and emotional costs for nothing.
Recently, the NFT royalty disputes are similar,
everyone wants to be prioritized in the transaction:
creators want a cut,
traders want smoother liquidity...
when congestion hits, whoever can afford the cost gets to go first.

Replying to what you said, "Then I should just always give the highest fee..."
I usually don’t do that either, it’s too exhausting.