Speaking as a formerly severely depressed person: yes, that fixes it.

I worked hard at it. I wanted to fix it. I didn't take any medications. It was very, very hard. I wallowed in it for a long time. I fixed it.

"Oh you weren't actually depressed then, you don't know what you're talking about." I was (severely), and I do.

I'm not going to say you weren't actually depressed, but your experience may not be representative. A broken leg may heal with positive thinking and effort, but most people will still want to get an x-ray and a cast.

It may not be very representative, I agree. I struggle with your analogy comparing broken bones to a broken mind. We have known for centuries how to fix a broken bone. We still don't have a 'cure' for depression. "Here, take this pill and feel numb for a few hours" doesn't really compare to an x-ray and a cast.

You're right, there's no obvious cure like for a broken leg. Perhaps cancer would be a better analogy. There are various treatments, sometimes they work, but they mostly suck and it's never certain. But regardless, "just don't have cancer!" isn't going to do it.