don't go too hard, and try to balance just below your lactic threshold throughout, if your legs are burning too much then back off a tiny bit rather than burying yourself and blowing up at half way.
Whatever you do you'll get a PB and something to aim at, oh if you have time to look at your watch on your wrist you aren't trying hard enough, mount it somewhere you can look at it safely if you must!
don't go too hard, and try to balance just below your lactic threshold throughout, if your legs are burning too much then back off a tiny bit rather than burying yourself and blowing up at half way.
Whatever you do you'll get a PB and something to aim at, oh if you have time to look at your watch on your wrist you aren't trying hard enough, mount it somewhere you can look at it safely if you must!