Some of the best ways to deal with negative people are to try to understand the reasons for their negativity, use "reverse psychology" and respond positively when they make negative statements, or to give them honest feedback about their critical statements. When nothing works, consider ignoring or walking away from people with a negative attitude. Sometimes it's just not worth dwelling on the negativity, particularly when one knows that the person isn't going to change.
Understanding the reasons why someone is negative is one of the best ways to deal with these kinds of people. In most cases, the negative behavior has its roots in a person's fears. These often include the fear of not being loved, of bad things happening, or of being disrespected by others. This negativity can manifest through judgmental comments, pessimism, being demanding or unreasonable, diffidence or the need to control others. Encouraging negative people to notice the sources of their negativity, as well as helping them realize that life is not nearly as bad as they think it is, can be an effective way to deal with the situation.
Alternatively, try to accept the negativity and hope things will improve, or seek the help of a counselor. Blaming the negative person is not likely to help, as negative people tend to be very sensitive to criticism. Dealing with a negative person requires patience, as it may take a long time to see any results.