The non-certificated pilot stated he completed an adjustment on the brake linage and taxied the airplane to the runway to test the brakes. The cockpit, before starting, and pre take off checklist were not performed. The pilot applied power after taxing onto the runway and the airplane became airborne. The nose of the airplane pitched straight up, and the airplane reached an altitude of about 30 feet. The pilot stated he attempted to push the control stick forward to lower the nose and was unsuccessful. The control stick was moved to the left and the pilot reduced the power. The airplane turned to the left in a nose down, left wing low attitude, and collided with the ground. The pilot exited the airplane, reached back inside the airplane, and shut the engine down. When the pilot was asked if he experienced any mechanical malfunction before the accident, he stated no, "It was a dumb mistake, I did not remove the seatbelt from around the right control stick."