Never again!!

I will never ever sell another house!! It is a very frustrating ordeal. We've been told that it isn't always this hard, but this has been one of the worst experiences of my life!! Two contracts have fallen through at the last minute...........like the day of closing. Today we found out that the appraisal came in $5000 less than what we are asking. Now a month ago the appraisal was at least what we were asking, if not more. The new lender wouldn't take that appraisal though. They wanted their own appraiser to do it. I swear that an appraisal is not really based on anything but the appraiser's opinion. How else would you explain such a big difference in numbers in just a month? It's all very frustrating. I'm almost to the point of never even buying another house.