Fear not! The way most credit card payments work, including our payment processor Stripe, is that an "authorization hold" is placed on your account for the amount of your payment. These holds can oftentimes look like any other pending transaction when viewing your bank or credit card statement.
In the case of a failed payment attempt, those holds will still show up; but since they did not go through on the site, no funds were actually transferred from your account, and you should see those pending charges disappear—typically within a few business days.
If for any reason you see legitimate duplicate charges on your account, please don't hesitate to open up a Help ticket and we'd be happy to issue a refund.