Change

A friend of mine asked how do you get a person with negative thoughts to change how they think.

I told him that they have to be a) willing to change or b) brainwashed.

I'm more for the willing to change aspect than the forceful brainwashing. Brainwashing is easy to do on most people, however if they have a strongly defined sense of Self than most likely regular and even some advanced brainwashing techniques won't work.

I think however if you approach the matter the right way you can get a negative person to at least try thinking in a more positive manner.

A simple exercise can be done to show them how. Have them keep a journal of their thoughts and experiences.

Then have them go back with a marker and highlight all the negative word choices and phrases. Then have them rewrite whatever possible in a more positive light.

That's one way, there are others. But thats a basic psychological technique used to treat people with depression and other psychological issues.

Also being positive relieves stress, generally keeps you healthier and happier as well.