Surely parental influence falls under environment?
This is why kids like to pretend to play kitchen or use a broom. They see you do it.
Anecdotally, I have seen children who have ‘bad attitudes’ do a 180 when the parents make an effort to model calmness and positivity. Anxious, stressed out or negative emotions in parents affect the kids.
In most settings, mood is contagious and is set by the leader. The catch is you have to keep it up.
I wonder if people who are more adept at creating and selective recall of memories tend to be happier individuals.