“I know what you are thinking. You are wondering, ‘How is it that he is so strong?’. The man smiled and tapped his finger against his temple. The reason I am so strong is because I think I am.” –Author unremembered
(Remind me if you know what book that quote came from).
In this case, the He would be She. The yearling is a filly.
An almost-yearling holds her own between a bossy two-year-old and a domineering older herd-mate.
Attitude and prudence is always a balancing act.