I think best life is as much a state of mind than a physical thing. Sure, those things we do physically are awesome markers however, if we apply the feeling, tone and mood of those things when we can't actually do them we can find a similar state of enjoyment and fulfillment. Or so I believe. I'd say you're doing fine River.
Absolutely! We do it without thinking, but if we paid attention to our breath more we have more control over how we feel, and can recognise how we might be feeling. Long, slow breathes can save us. I remember learning the yogis saying we all have a certain amount of breaths allocated to us in our lifetime. I thought it was hogwash but if you think about fast, shallow breathing - that shizzle ain't gonna have you live long.
I've never thought of it this way but it makes sense. Deep breathing can be awesome so who wouldn't want to do more of it?