Was this after a layoff? You did say you're just coming back to the trials, right? I find whenever I come back from a layoff particularly after getting hurt), I ride like a wuss until I get in some saddle time. If it's not a matter of saddle time, consider investing in some pads. Something like kneepads or a knee/shin system might give you a confidence boost. I'm more willing to commit when I'm wearing kneepads, not because they'll protect me from every injury, but because they just give me that little confidence boost (or false sense of security/invincibility, I'm not sure which one). Chelboed's controlled environment idea would also be great for confidence and getting comfortable on your bike again.