https://www.youtube.com/watch?v=JvEas_zZ4fM&t=21s
One of the points he makes is that you should think about stocks as businesses. Instead of "I bought a stock" think "I bought a business". That puts you in a better frame of mind and perspective for the long term. i.e., You don't buy or sell a farm based on today's headlines.
The real question is whether things have changed on a 5, 10 or 20 year time frame for the businesses you hold.