Miners pick transactions largely by fee rate, measured in sats per virtual byte. If yours pays less than others, it waits. Nothing has been lost: an unconfirmed transaction has not moved your coins yet.

Check it first

Paste the transaction ID into a mempool explorer and compare its fee rate with the current recommended rates. If it is close to them, patience is often enough. If it is far below, or below the minimum relay fee, it may wait a very long time.

Your options

Replace-by-fee (RBF): if you sent it and your wallet supports RBF, use "Bump fee" or "Speed up". This sends a replacement with a higher fee.

Child-pays-for-parent (CPFP): if you are the receiver, or the transaction has change returning to you, spend that unconfirmed output with a high fee.…