If you know exactly why you are selling, then it is easier for you to set the right plan of action to get what it is that you want.
If you are a seller who needs to close a sale as quickly as possible, then you should know that getting the highest price possible is not one of your priorities. It does not mean that you won't or cannot get the highest price, but it means that the price is not the deciding factor. A buyer who can give you a quick closing time will appeal much more to you than a buyer who can offer you more money but the negotiation and closing time drag on.
Once you know what your limits and reasons are, discuss them with your agent so that they can help you set your goals realistically. If you decide to list your home on your own, make sure you do research on the current market, and you get the proper advice you need in terms of legal issues, etc. The key is to be realistic and to know what your goals are so that they can be met.