Stoic philosophy emphasizes living in the moment. Bad times are inevitable, so instead of complaining, do your best to have an internal locus of control.
Only recently, after listening to a very captivating podcast from Tim Ferris, did I actually learn what stoicism was, as well as how stoicism, martial arts and BJJ competition, and everyday obstacles are related.
For a more thorough read on stoicism, I have to refer you to Ryan Holiday’s bestsellerThe Obstacle is the Way: The Timeless Art of Turning Trials Into Triumphs. He does a very thorough job of articulating stoicism in a very enjoyable and easily consumable manner.
These two sources of stoicism I stumbled upon caused me to reflect a lot on how closely these principles apply to life as a martial artist and as an athlete.