Mailbag: Can physicality, discipline be coached?

I keep hearing the teams who made the playoffs are more physical and more disciplined than the Cowboys. And stats like ranking among the worst in the league in penalties and missed tackles seem to support that. But can physicality and discipline be coached? Seems to me you either have that mindset, or you don’t. Which means, do the Cowboys need to take a hard look at the players they have on their roster?