Example 1: 

My daughter Isabella is 17 years old. She just graduated
from high school and I am worried about her. The thing is, she has never dated anyone. All her friends
have gone on dates but her.
Should I try to help her? Or should I let
nature take its course?

Example 2:

Ted: My friend didn’t
study at all last term for his algebra class. I took the final exam one day
before the rest of the class. After the exam, he wanted me to give him all of
the answers.

Irene: He wanted you
to cheat?! Well, did you give him the answers?

Ted: Oh, no. I let
nature take its course: he failed the exam.

Meaning: To let nature take its course means to let things happen
naturally with no interference from an outside source.

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