Nerves come from lack of experience. Experience comes from lack of nerves!
Seriously though, just keep putting the plane in the air, flying it, and you'll relax. Learn to "get in front of the plane" rather than just throwing the sticks around, and you'll build confidence faster. Have a plan when you fly. If you just go up, keep the plane from crashing for a few minutes, and then land, it will take longer to build the skills it takes to have confidence in your skills. Have a constant preflight routine that includes a thorough preflight and post-flight inspection, and you'll gain confidence in your equipment.

Brad