Just can't keep a stable flight

[loop_n_roll 7]

I've had this plane several months and find I just can't keep it stable in flight. Trimming for level flight, take my eyes off for a second only to find the plane in a climb or steep dive. I have the CH Eclipse yoke and CH pedals. What am I doing wrong here? Criticisms accepted without malice. I think if real flying were this difficult no one would do it.