So sorry to hear this man, it's a shitty road to be on. I have not had it first hand with my wife, but several of my family members have had their bout with cancer. What was said is best, try to be supportive, staying strong for her, keep stress off of her.
But when it comes to you, leaning on your friends and family is what its all about. People will be more than willing to help if you just ask. Even if it is just to vent, don't bottle it up, as it will only make more stress for you and her.
Outside of mental support, physical support is one of the best things you can focus your efforts on. There will be days where she is just not up for anything including taking care of herself. Even the littlest things like a piece of chocolate or some pediasure when she really doesn't have an appetite. Or drawing a bath for her when she's feeling achy. Consuming your efforts into helping her will go a long way for the overall morale.