This was the most helpful advice I got from the lactation consultant. It's a terrible feeling to pump while your baby is screaming. It leaves you impatiently staring at your boobs the way you would when you watch water boil. Rather than stressing myself out about pumping for the current feed, I'd tell myself that my daughter would get what she needed, that she'd be OK, and that whatever I was producing would get bottled for the next feed. It helped me stay relaxed and present.