Here's your lesson on Solana priority fees and transaction failures. Solana validators process transactions in bundles, and when the network gets busy, your transaction might not make the cut if you're not offering enough incentive. A priority fee is extra compensation you pay to validators to bump your transaction up in the queue, separate from the standard network fee. If you don't include a priority fee during high congestion, your transaction can timeout and fail without ever settling on-chain. You're not losing SOL in this case—the transaction simply expires, usually within 90 seconds, and your funds return to your wallet. The tricky part is that optimal priority fees fluctuate constantly based on network demand. A fee that works fine at 2am might not cut it during peak trading hours. Most modern wallets and dApps now estimate priority fees automatically, but sometimes the network moves faster than the estimate, and your transaction still fails. Don't worry—you can always resubmit with a higher priority fee. When competition is fierce, even the toughest transactions need backup.