Recently, while accompanying a rather talented athlete during yet another difficult training session I'd prescribed for her, I was informed that she 'hated me'. Now, after having finished the difficult session and having come to her senses, she did 'take it back'. Actually, I believe she appreciates the rather huge increase in fitness she's witnessed recently.
After almost 8 years I've been coaching endurance athletes, I still favor the approach of 'raising the left to drag the right' up with it. Granted, training over on the left is less comfortable, and it requires a great deal of attention to stress and recovery, but it provides with it a constant reference as to fitness and adaptation. It's pretty easy to heap tons of 'crap miles' onto an athlete. Athletes can swim, bike and run "L2" for months straight every day... toss in some high L3 through L5 and you immediately know A) how fit they are and B) how tired they are. I also find it so much easier to plan peaks for important races for the very same reasons. If all you ever do is train long and slow you get good at going long and slow.
So, to those that call me 'coach'... hate away.