Some houses are so desirable that people line up to buy them. If your house is average, that doesn't mean that you must settle for an average price.
Some houses sell for more than their seemingly similar competition.
The real estate market is cyclical from year to year and even from season to season. Its down periods are almost always followed by ups. Also, some seasons are better for sellers. Spring is usually active while major holiday periods are quiet. The pattern will vary from place to place.