How do psychologists help people who are special needs who are unhappy with life because they are special needs and have many limitations?

By helping them shift their focus away from what they aren't able to do and on to something that they can do.

They try to make them focus on what they CAN do. Look, none of us can do everything we want to do- we all have limitations. I understand that some make living in the world more difficult. But many people with limitations have made names for themselves by finding ways to overcome those limitations. Go watch Temple Grandin- a movie about a woman with autism who got a Ph.D. and became famous in her field. 

Everybody has problems, no matter what their own situation or ability. Figuring out how to solve your own problems is what makes life interesting and gives you a sense of accomplishment. Indeed, fixing a problem is, in fact, the definition of fun.

I would rather rely on friends or myself than having to deal with a heartless lier.