During the eBay bidding process, each and every bidder is alerted to the fact that they are about to place a bid that is considered to be a binding contract between the buyer and seller and eBay. You may not cancel/delete/rescind this bid in the last 12 hours of the auction per the eBay rules and it is your responsibility to cancel it prior to that time. Each bid placed by you causes other bidders to decide to increases the price they are willing to pay for an auction item or to drop out of the bidding process.
eBay has decided it is unfair to the seller and the other bidders for you to drive the price up for other bidders, and then ask to have that bid removed on short notice, thus the 12 hour rule and the no canceling the sale after the close of the auction rule is in effect as well. We do not cancel auctions per the eBay rules.