If your house is not priced competitively, people looking in your price range will reject your house in favor of other, larger homes for the same price. Overpricing usually increases time on the market, and that adds to the carrying costs. Ultimately, many overpriced properties sell below market value. Buyers look for homes, not houses, and they buy the home in which they would like to live. If you were selling a car, you would wash it or maybe even detail it to get the highest price.
Houses are no different.
It's difficult for them to do that if you follow them around pointing out every improvement that you made. It may even have the opposite effect you want, by making them feel they are intruding on your private space. Resist the temptation to talk the entire time a buyer is there, and let them discover things on their own. Try a tasteful sign to point out some hidden amenity that they might miss. Property owner should leave the premises when your property is being shown.