Excellent, I'm glad that's been your experience. Mine hasn't been like that and I've waded through too many everyone's-so-friendly-and-getting-nothing-done-and-always-stressed teams with weak leadership and low standards. I'm hoping that your experience is more typical than mine!
It's not typical. But when it's not, lack of #1 and sometimes #2 is the key missing ingredient, not an aggressive churn through new hires until the perfect combination of employees is found.
1) A shared goal and a leader that maintained focus.
2) Baggage checked at the door.
3) Adequate resources and skills.
4) Good humor.
Nobody ever had to get fired.