With some highly optimistic agents this may be an honest onetime mistake. Buyers compare price, features, location, and condition of all the homes they inspect. If yours is priced too high, it will not compare favorably with others the buyers look at. Your competition has more to offer for the money. Your home will not appraise at or near the asking price.
Most buyers require mortgage financing and that means an appraisal by the lender.
Appraisers look at similar homes in your neighborhood that have sold in the last six months. If you have a 3 bedroom ranch, it is not equivalent to a 4 bedroom colonial. No matter how much you love your house, the appraiser will not see it with the same nostalgia. Your buyer can't get a mortgage. You eventually sell for less than market value.