I have read about the “act-to-become” principle.
Our modern culture is often obsessed with the idea of “authenticity” (even though when pressed, they’re probably not sure what it means), and the idea of acting in a way you might not really be feeling is criticized as fake or manipulative. But the best way to change your feelings is to first change your behavior.
Quoting W.H. Auden: “Human beings are by nature actors, who cannot become something until first they have pretended to be it. They are therefore not to be divided into the hypocritical and the sincere, but into the sane, who know they are acting, and the mad who do not.”
So be real and act your best, yo.