nafun

Yesterday i set my bike up on the trainer for some intervals. My planned workout was:

15 min warmup
1x10
5 recovery
4x(3+3)
5 recovery
1x10
warm down

For these intervals, i was using my speedometer to hold constant power, as my trainer has a reasonably consistent resistance curve.

On the first of the 3 minute intervals i hit my observed Max HR, and held it for the last 15 seconds of the interval. On the second interval, i again hit my Max HR, but this time for the last 30 seconds of the interval. I was able to maintain target speed on both. On the third, my form was noticeably deteriorating, and my speed would drift down every time i took my eyes off my cyclocomputer. I finished the interval, kicking the speed back up every time i noticed it decreasing, but i guess the average power suffered as my HR did not get quite as high.

I called it quits for the 3x3's after the third, and when i tried to do the last 10min, i had nothing left and aborted after 2 mins.

So, my question is:
Was this too hard, unnecessarily fatiguing myself preventing the completion of the workout?
Or was this just good training / overreaching?