The mental side and work ethic are huge pieces of this. Playbooks are one thing, but studying film, knowing the reads and doing the work away from practice.
The personal part of it to, sometimes these kids have a lot of hanger ons that are in their ear telling them what to do. Or they are out partying and not focused on football. Dion Jordan was just in the news on this piece.
https://www.nbcsports.com/nfl/profootballtalk/rumor-mill/news/dion-jordan-accepts-full-responsibility-for-his-wasted-playing-career
It will be interesting how NIL and these guys having money before they get to the league if it makes it any better