How to set challenging yet attainable goals?

It is absolutely certain that you never achieve more than your goals. Experiments testing this thesis have shown it to be true. Surprise! At the same time, you must ground your goals in the real world, otherwise you’re just daydreaming.
If you’re asking $525,000 for your house, and no house in your neighborhood has ever sold for that amount, you’d better have some good reasons for setting your goal that high. Maybe you’re in a rising real estate market. Maybe your house is larger or noticeably nicer than any other house in the neighborhood. Maybe a state-of-the-art shopping center is under construction nearby, making your location more desirable than ever before. Any of these factors make a record-breaking price for your home attainable. Without special factors like these, you’re wasting your time by starting with such a high goal. Likewise, you want to be sure that the $525,000 is challenging. If every house on the block sells for $525,000, that price isn’t much of a goal — unless your house is noticeably more run-down than the others (in which case, you may want to consider some landscaping or painting first). You may have to do some research to find ways to justify asking a higher price than the others in the neighborhood. If you find out that major construction is planned for the near future, for example, you can make that part of your sales pitch. Too many of us suffer from setting our goals too low. Shoot high or not at all — you can be sure that the other side will never ask you to raise your goals. But remember that you don’t have to become rich and famous before breakfast. Goals that are too high for the deal lead to frustration and failed negotiations. For the specific negotiation at hand, consider the marketplace, current values, and your available options.
You can quickly see that setting a challenging yet attainable goal requires that you have a good deal of information — information you always need before you start negotiating. Setting your goals is one way you know whether you’re prepared for your next negotiation.
Think of that big thermometer the United Way puts up before every fundraising drive. The number at the top of the thermometer represents a figure generally a little higher than the previous year, but not too much higher. A better economy, more members participating in the fundraising drive, or a special event (such as building a new recreation center) justifies an increased amount. As group members raise money, they fill the outline of the thermometer with red paint to show exactly what has been contributed. Whether the organization reaches its goal or not, the thermometer looks very red at the end of the campaign, and those who contributed feel good.