I've always struggled with depression. And my husband has it in his head that he is the key to my happiness, and if I'm not happy, then it's his fault. He thinks the fact that I'm depressed (even though I was this way before we ever met) is somehow his fault and means he's failed as a husband. Here's the conversation:

Him: It's a hell of a lot more than inconvenient to know you're single handily the result of someone being depressed. You don't know what it's like to carry around that wiegt. I try to be happy. But it just beats me down every day to see you unhappy. It's my job to make sure you're happy, and I'm shit at it

Me: ok, I'm going to say this once, and only once, so listen up. You need to get this into your head. YOU ARE NOT THE CAUSE OF MY DEPRESSION. THEY HAVE NOTHING TO DO WITH YOU, AND NEVER HAVE. THIS IS IN NO WAY YOUR FAULT

Him: I don't believe that at all

Me: I was depressed long before I met you. These are issues I developed very young. The fact that they didn't disappear the second you walked into my life has absolutely nothing to do with you

Him: It's my job to make sure they go away and you're happy

Me: You can't do that. That's not a fair expectation to put on yourself

Him: Then I'm not good enough. And I know rationally you're right. But mentally and emotionally, I can't

Me: That's not true. I would be in worse shape without you. At least with you, I have happy moments. And that's a hell of a lot more than I could say of my life before I met you

Him: I just can't believe that

Me: why not? I don't understand

Him: Look, if you want to understand me, you need to know how if feel. It hurts to know I can't make you happy

He blames himself, and he's hurting. How do I help him realize it's not his fault?