Study freedom. Freedom of movement, freedom of imagination, freedom from fear. This is what is in great playing of all kinds. The irony of course is that freedom is already within us, but we block ourselves from it more often than not.
When most people being to play music, it's a joyous challenge. We feel free to explore it, to make mistakes, to try new things. Over time, we learn rules, and they begin to constrict our freedom. We learn what is so-called "bad" and "good" and focus on judgement rather than playing. Let yourself play and don't worry about what happens - just play. Practice that mental state. When I see the children play in the park near me, they play freely. If they fall, they fall - and then get up and keep playing just as hard as before. That is freedom.