There are few people who want to admit a date is a failure, but it is generally obvious to both people when it is not working for them. Rather than suffer through hours of painful conversation, it is best for one person to step up and admit they are not having a good time. The person who is honest enough to admit this will save themselves from hours of wasted time when they would rather be elsewhere.
Confidence is important when dating, and a person with plenty of confidence in themselves is able to state they do not want to be with someone. Those who prolong bad dates often feel obligated to go through with it, and they are doing nothing more than wasting their time as well as that of the other person. Honesty is the best policy in this case, and it should be used in a firm but gentle manner.