Simple...?

I saw a child aged around one year-old plus. She was so cute and sweet with a pink dress and a hat on. Looking at her enjoying the leisurely walk without care around the temple, I told myself why couldn’t I think and act the way she is – just be simple!

What does simple mean?
Does it mean you don’t have to think? The least not too much, though.
Does it mean that you follow your first instinct and just do it?
Would simple make the simple way for you?
Would simple make you look like a fool?
What's the standard of being simple?
How to be simple in simple way?

oh...Simple simple as it goes...
I'm still learning to be simple in all aspects of life :D