I can feel my heart beat

Babies that are born close to full term sometimes get in more trouble than babies born more preterm. This may seem odd and the reasons are many, but one problem in particular has to do with the muscles surrounding the blood vessels in their lungs. See the very premature babies (less than 30 weeks) do not have much in the way of a muscle layer to their blood vessels. Late preterm babies (34-37 weeks) and term babies have well developed muscular layers to these blood vessels. And when the baby develops acidosis or low blood oxygen, which occurs if they have any respiratory illness, these blood vessels clinch up and close off blood flow to the lungs making the baby even sicker. This is called pulmonary hypertension and can be fatal.
Megan was born at 36 weeks and immediately started having trouble breathing. We placed her on oxygen blown up into her nose at high pressures. This allows her to breath more easily and increases her oxygen to help those blood vessels relax and open up. Well, she did well for about 24 hours and then I get called to her bedside because her oxygen level suddenly dropped. I walk (quickly) to her bedside and when she breathes I can see her pulling hard. The nares of her nose flare out and her belly caves in as she is using her abdominal muscles to help pull air into her lungs. I listen to her chest and while I can hear good breath sounds on her left side, I hear none on her right. On 100% oxygen her oxygen saturations stay in the 70's. You and I would be at 100%. Most of us get air hungry at 92%. I can see that she is hurting. I give her ativan and morphine to calm her down and ease her pain. I place a light against her chest and the entire right side lights up in a faint red glow. She has a pneumothorax. A pneumothorax is when a pocket of air has formed between the chest wall and the lung. It will push the lung over and can eventually collapse it.
So the baby is not doing well and we do not have time to confirm this with a chest x-ray so I ask the nurse for betadine, a butterfly needle and a syringe.
I pick the spot on her chest where I know the needle should go. I sterilize the site and we insert the needle. 80 cc of air comes out and her oxygen sats rise to 100% and she begins to breathe comfortably.
I have done this so many times before that I remain calm throughout. I could be ordering dinner off a menu. My pulse, naturally low stays in the 50's and my hands remain steady. I never raise my voice or even hint at the urgency that we all know exists.
So jump to my home where I am helping my seven year old with math. The problems involve counting by threes and I know Marcus knows how to count by threes. We work on problems for twenty minutes and I ask him what six plus three is and he says eight. Well I tell him "You know what six plus three is, we have been doing this for twenty minutes Marcus. One two THREE, four, five, SIX, seven, eight, NINE." So what is six plus three. And he says "Four". And I can start to feel my heart racing and I find my voice becoming much sterner and louder than I want.
So tell me how come I can stand at the bedside of a critically ill newborn without the slightest change in my emotional state but twenty minutes into homework with my son and I am a mess. It doesn't make sense. I am supposed to have perspective.