[oldkim]

Breathing is very important when it comes to rifles but for the most part it's not that for pistols (again unless for Bullseye shooting).

For rifles since the third point of contact is your shoulder - your breath control will actively impact your shooting.

For defensive or target shooting the other fundamentals need more priority (stance, grip, sight picture and trigger control). Breathing is somewhat important but you can offset with your arm movements.

Unless your a marksman shooting at 25 or 50 yards and placing shots of 2-4 inch groups than breathing is not your most important factor that you need to work on for pistol shooting.