City Slickers with Jack Palance (Curly) and Billy Crystal (Mitch).
I cannot find the complete text of the speech but starting at 2:08 in this Youtube clip. Below are two portions of the text.
Normally in most of the movie speeches I post the Youtube Clip after the text, because I find the words the most important part, but since I cannot find the full text I put the youtube clip first in this case.
Mitch: You ever been in love?
Curly: Once. I was driving a herd across the panhandle. Texas. Passed near this little dirt farm right about sundown. Out in the field was this young woman, working down in the dirt. Just about then she stood up to stretch her back. She was wearing a little cotton dress, and the settin’ sun was right behind her, showing the shape that God had give her.
Mitch: What happened?
Curly: I just turned around and rode away.
Curly: I figured it wasn’t gonna get any better than that.
Mitch: But you could have been, you know…with her.
Curly: Been with lots of women.
Mitch: Yeah, but you know, she could have been the love of your life.
Curly: She is.
He talks about how people get themselves tied up in knots and then gives the very important secret of life to his younger traveling companion.
Curly: Do you know what the secret of life is? [points index finger skyward] This.
Mitch: Your finger?
Curly: One thing. Just one thing. You stick to that and the rest don’t mean shit.
Mitch: But, what is the “one thing?”
Curly: [smiles and points his finger at Mitch] That’s what you have to find out.