I ran a 5:05 mile on Monday on the track, but then yesterday I ran a 18:19 5k at a cross meet (PR from 18:28 flat course at the beginning of the race season). It had a few hills but there were two big downhills and a few uphills (it's generally a fast course). In the summer, I was base building up to 40mpw and have been at 30-35mpw since then until the last week or two (dropping for speed work). Considering my 800 is a 2:17, I'm not really a speed heavy guy. My splits were 5:37, 11:35, 18:19. The first mile felt fine, and I tried to hold back but it was fast, and I ran with a teammate the 2nd mile which might have slowed me down. We did a fast type of 800m workout Thrusday and then 150m sprints Friday. Typical workouts all year have been mostly 800m repeats (lowest @ 2:48 pace) and few 1000m repeats at the same pace. Why can't I break 18? I am 16yo/male/sophomore.