Cancel Opensea transaction?

I tried to buy an NFT on Opensea and I put my gas price at 20 Gwei. I now know that that was a pretty big mistake I've waited a day for the transaction to go through and honestly I don't think it ever will. I've contacted support on Opensea to try and get the transaction cancelled but is there any way of doing it myself? Opensea support might take a week to respond so thanks in advance for the help