The certificated private pilot performed a "normal" landing at 60 miles per hour and the tail-wheel-equipped airplane continued for approximately 600 to 700 feet on the 2,215 foot-long by 70-foot-wide turf runway, before it drifted to the right. The pilot was unable to correct the drift with left rudder and left brake before the airplane departed the runway, and struck trees at approximately "30 miles per hour." When asked how the accident could have been prevented, the pilot stated he should have kept the control stick fully back during the landing roll, and that the wet grass condition significantly decreased surface friction available for braking and steering effectiveness. Calm winds were reported 5 nautical miles southeast of the airport. Examination of the airplane by a Federal Aviation Administration inspector did not reveal any evidence of preimpact mechanical malfunctions.