Cancellations should be rarely used, if ever. There are members who have been on Ebay for several decades and have not cancelled an order.
First of all, the cancellation is not an instruction, nor is it guaranteed. It is a request, and the seller can accept or decline the request, as you know. Ebay gives the seller three days to make that decision. In fact, some sellers cannot process a cancellation even if you do it immediately. The order is sent immediately to the Shipping Department and it cannot be retrieved from the flow.
There is so much more than just cancelling your order here. Seller incurs immediate fees, has to deal with your request, has lost the time involved in that listing, and taken their inventory out of search for no good reason.
On every page, whether you are bidding or buying, it says that you are entering into a binding contract to purchase the item. So you need to not purchase unless you are sure that you want to buy.
There was a recent post by a buyer who got put in the High Risk Buyer Program that Ebay runs. If you exhibit bad buyer behavior, frequent bid retractions, returns, and/or cancellations, you are put in this program and can only buyer fixed price, immediate payment required listings, until Ebay deems you have learned good buying behavior.
