Anxiety, anger, and pain share some circuitry in the brain. If you're feeling like you're going to have a short-fuse (easily angered) day with your kid, pop one ibuprofen. I found it helped replenish the zen/chill reserves immensely when I really needed it. But watch your total consumption of all pain killers; they do cumulative damage to your liver.
Even if you're somewhere in the middle, don't let the baby crying stress you out. It's obviously some sort of instinct that your crying child triggers, but really, they're not gonna die if you let them cry for a few more minutes. With my first child, whenever she cried, I got really stressed out and tried to figure out and then accommodate her as quickly as possible, as if every second counts.
Take your time, especially if you're easily angered, like the parent comment mentions. If your baby just won't stop crying no matter what you try or do and you feel like you might be losing it, just put it back in the crib, leave the room for 5 minutes and come back when you calmed down.
