Thanks for your honesty. I would recommend taking a skills class if any are offered in your area. Aside from that, ride on mellower stuff to start so you can relax. Don't ride trails too far beyond your current skills just because your more experience friends are. Equipment-wise, do you have good knobby mtb tires at the proper psi? Proper tires and psi provide help comfort and confidence. Back to skills, I would recommend learning the Attack Position (look it up on youtube or see LeeLovesBikes.com). It's like an athletic ready position in traditional sports but it's the mtb-version that gives you confidence and control.