This brings back very old memories. When I first began singing, tentatively at first, I had not learned to breath from the diaphagm. I was self-taught mostly, listening to and emulating those whose phrasing and vocal quality impressed me; not imitating so much as trying to see how they used their voices to such good effect.

I was fine until I started having to sing while playing an instrument at the same time. I found myself lapsing back into shallower breathing and losing my phrasing until I disciplined myself to focus on singing properly while seated and holding a guitar. Posture, I found, had a lot to do with it. Leaning over the instrument tends to make me a little lazy and take away some depth. The other handicap was that tentativeness, or shyness I felt - a reluctance to sing in full voice. Once I pushed through that fear, it helped a great deal.