Most people already set it in their minds that they can't run a mile, that it would physically be impossible for them to do so.
I've heard, "I will die", "My legs will fall off", "it will take me hours to run 1 mile"
1 mile can sound pretty daunting,
But instead of thinking in terms of Distance, just go for Time.
"Today I'll run for 5 mins."
"Today, I'll run for 10 mins"
"Today, I'll run for 15 mins"
It doesn't sound so bad right?
And the plus side, usually people can run 1 mile in 15 mins or less, so you've conquered your greatest feat in just 15 mins.