often when i'm doing something specific (such as hill repeats, intervals, etc.) i have a certain number of repetitions in mind and i usually try to complete them all. naturally i start to get tired and slower toward the end. sometimes i get a little nauseous or light headed but i feel compelled to keep on.
however, is doing too much ultimately hurting my performance? for example, am i gaining anything by struggling up the hill at 25% reduced speed for the two reps? or am i just wearing my body down needlessly?
i know that more training isn't necessarily good training. but how do you know exactly when to call it a day and head home?