Considering I’ve been a runner since... 5th grade, ran track/XC throughout all of HS/most of college, have run in a dozen half-marathons, more 5/10K’s than i can remember, and 4 marathons, and I STILL can’t break that damn 4-hr marathon barrier (4:02:00)... yeah, a 3:45-marathon for a “casual” runner is downright…