Honestly, I think it takes a critical combination of these things. I am nowhere without a good groom and management, and I could not improve without a coach that pushes me.
My progression has been dependent on surrounding myself and my horses with the best team of professionals and program.
I would say the key for me, though, has been the consistent support I have received from my family. Since I was 6, they have done everything possible to enable me to pursue my passion.