The one thing
#Truth from the movie City Slickers:
Curly: Do you know what the secret of life is?
Mitch: No. What?
Curly: This. [He holds up one finger.]
Mitch: Your finger?
Curly: One thing. Just one thing. You stick to that and everything else don’t mean shit.
Mitch: That’s great, but what’s the “one thing”?
Curly: That’s what you’ve got to figure out.