What Is The Point Of Prayer?

[Whateverist]

Assuming atheism for a moment....I pose a question:

Does the atheist determine what is meaningful for the Christian and vice versa. ..

Or...

Does each individual determine what is meaningful to them?

Not sure why you should need to assume atheism to pose or answer this question.

Of course is it up to each individual to find what is meaningful to himself. No one else can determine that for us because there is no objective measure by which an outsider can verify the fit.