There is a 5000 years old epic called Ramayana which dedicates a significant part of it to a conversation between the protagonist Ram and his guru, agastya.

The summary of that entire conversation is this:

If you ever feel demotivated, defeated or dull just pray to the sun or go into the sunlight.

This message was repeated dozens of times over and over with various metaphors.

I think they were trying to hammer the point that sunlight solves a lot of issues.