the other day i did some hills, and was feeling pretty good until when towards the end of the last few repeats I just crashed near the top of the hill each time. then 3 days later i tried 800mx8 repeats and it was basically the same story-on pace until about the last 300m of the final 3 repeats where i suddenly feel like a freight truck hit me... ive been running high mileage. in these workouts it doesnt feel like im really in major oxygen debt, just all of a sudden it hits me like a brick wall and i slow down considerably and cant respond at all. my easy and uptempo runs I have felt great for the most part though; any insights on what i could/should do, or am I in for a bad indoor/winter road race season based on this sudden crashing in workouts??