Well said mateNever let a win go to your head. Never let a loss go to your heart.
Fix your brain. Loosing isn't the issue the emotional response is. Because it clouds you ability to focus. Wastes energy and wastes the energy of people trying to prop you up.
Being positive and upbeat in adversity is a discipline issue. Which will fix under enough adversity. Provided you are mindful of it.
Dude broke his leg in a kickboxing fight and recovered physically and mentally.
And look you won't get it in one day. It is a developmental process. But the sooner you start working on it. The better a martial artist you will be.