The pilot reported that he was practicing takeoffs and landings in the traffic pattern when the accident occurred. He noted that he did not follow his normal routine, which was to lower the landing gear prior to the wing flaps while on downwind leg; instead he lowered the flaps. At that time, he noticed that the airspeed was low. The pilot stated that he subsequently became fixated on maintaining airspeed and did not notice that the landing gear was not extended. Additionally, he did not complete a before landing checklist. The pilot noted that there were no failures or malfunctions associated with the airplane prior to the accident. The airplane sustained substantial damage to the fuselage during the gear-up landing.