My husband is so negative

You know how they say that we are the product of the 5 people we spend the most time with? Well, 3 of them are my husband, my preteen and my teen. And they can be SO negative! I kind of expect some of the teen angst and attitude from my son, but it’s really my husband who is so discouraging. He’s clinically depressed and in therapy but he is so negative about everything. When we met years ago he was so happy-go-lucky but now he’s a completely different person. He has forgotten how to relax and is so anxious all the time. That’s one issue. The anxiety just vibrates off him all the time. As I’m going through SCS and doing my own thought work, I’m trying to change my thinking about a lot of situations. I have been trying to share the Model with hubby in hopes that he can use it on himself and he refuses to validate any of it. Instead, he tries to purposefully dispute any of the positive thoughts I’m trying to practice. It feels like every time I make a positive statement, he will counter it with a discouraging one. I know this is a reflection of his own mental state and I don’t have to agree with him, but I’m wondering how you protect yourself against negative people who are in your life all the time? I can’t spend enough time with upbeat people to make up for the time I spend with my husband. I do love him and he’s an amazing person, but he’s been going through this gloomy period for over 10 years now. Therapy doesn’t seem to help him, and he’s unwilling to do anything else like listening to the How to Feel Better course or reading self-help material. The therapy is so passive, he just goes a couple of times a month and bitches about his life and the therapist just nods and doesn’t expect anything of him. So he’s not changing. I married a happy guy and now I have Mr. Doom and Gloom most of the time. How can I stay in a state of positive energy and vibration in spite of being around someone negative all the time? Thank you!