I'm not sure if I can handle my wife's mental illness anymore. I'm so tired of it.
That does sound tiring. What sort of mental illness does she suffer from?
I don't know exactly, but she goes on long rambling speeches.
I'm sure that's difficult, but you should be supportive of your spouse with her issues. She will look to you for comfort and you should be there to help her out.
It's no use I've just given up.
I don't think you should give up on your wife. It might be a good idea to convince her to see a professional who is trained in helping people who suffer from mental illness.