The Ethereum blockchain may sometimes have unpredictable upswings in gas fees - the transaction fees that are dictated by demand for blockspace, and how congested the network is. This is especially the case on Layer 1, where gas fees can be much higher than Layer 2.
Sometimes, when submitting a transaction on Layer 1 during times of very high network congestion, you'll find that your transaction has been "stalled" - this is due to gas prices increasing significantly higher than the gas fee you specified, effectively putting you behind a long queue of transactions the network is trying to process.
To cancel a stalled transaction, visit the Activity tab of your wallet, where you can see the stalled transaction. Select it and then select Cancel, which will allow you to pay the gas fees required to cancel the transaction.
Note: Canceling a transaction costs gas fees. Because transactions on the blockchain are irreversible, the only way to cancel is by sending another transaction with a higher gas fee, effectively overriding your stalled one.