Mindful is a very short game that is difficult to review without creating spoilers for the story.
I played it without any context other than knowing that the author who wrote it also wrote one of my favorite 2018 games Animalia. Suffice to say I was ill-prepared and I'm very glad I was because I feel like I had the emotional experience the author intended for the piece.
So, don't read too much about Mindful before you begin. Just experience it as it is and enjoy the ride.