To understand this video, please go to this article and you’ll understand the importance of nose breathing, among other things, for confidence.
https://benoitfoucher.com/5-breathing-exercises-to-develop-your-confidence/
Also, to go further:
– attend Pavel Tsatsouline Strongfirst’s seminar Second Wind, or online course Second Wind Express
– read The Oxygen Advantage, by Patrick Mc Keon