I get the gist of this post. I also suffer from GAD and depression. I can only help by stating how I think my heart helps my depression and anxiety. I am a very spiritual person and I use many tools to help my depression and GAD to include

Eating right......brain help here.
Supplements ( omega 3's) .....brain help here

Meditation...spiritual help here and warms my heart.

Being social.....warms my heart....gives me hope.

I guess what I am saying is I believe that we are more than just our mind (Brain)

We are spiritual (directly affects my mood) ... higher power
We are physical (directly affects my mood) . ...nutrician
We are a brain (thinking directly affects my mood)...training our thoughts

I can't be scientific here. I just know what has helped me.