The point is a lot of teams do fine in the playoffs, so only the Cowboys get the excuse of limited practices and stuff? No, it's mental toughness and eating the cheese that Jerry offers. They go in overconfident and underprepared and fold when hit in the mouth..every.single.time.
Preparing isn't just practice. It's taking personal time and studying the opponents films. It's looking for weaknesses that you can exploit. It's about finding everything you can about the tendencies of the guys on the other side of the ball. That's not just on coaches. Every player hungry for a championship should be doing it.