Loomis, Yoga, hell yeah. I use it every time I put. Rooting down and reaching out in all directions. And as Vince mentioned: breathe! Yes, it is great.
Technique and practice. Technique and developing a personal routine is huge. I am not great at disc golf, but far from crappy, and I have found that finding what works and sticking with it is how I improve. All of the feedback here has some truth, especially what Palmer said
I just go out and try new shots. If they work, I start to work on them. The same with putting. I have two putting styles I switch between depending on the conditions and the shot. But most importantly, I always follow my routine.
The number one thing is attitude, previously mentioned as confidence. Why do you think Pros tell Ams to play up? To learn the winning attitude. I stay in shape and work had at everything I do because my attitude informs my performance. I have beat too many players because I crushed their head game with my winning attitude.