I went to the gym tonight and pushed myself too hard on the treadmill. Currently following the RW half marathon schedule I was down for 6x 800m at 5k pace. I had to give up after 4 intervals. Previously I've been able to do the speed sessions alright.
Question is - if I'm struggling should I:
a. decrease the speed
b. increase the rest periods
c. shorten the work periods
or some combination of above?