Whenever you submit a transaction, it competes with other transactions to be added to the blockchain. To decide what is included, every transaction must pay ‘gas.’ Because of this, the amount of gas needed for a transaction to execute depends on network demand.

If your gas priority is not high enough -or if there has been a surge in demand on the network- it might take longer for the transaction to be executed. This might even make your transaction fail.

If you want to know how to cancel or speed up a transaction, visit this article.