Here’s how I explain it…if you were going to drive from Boston to LA you’d want a map and you’d work out your basic route before you left, right?
You wouldn’t plan every stop for gas, cos you wouldn’t know when you were going to run out! But you would probably try to plan where you were going to sleep each night.
You’d have milestones on the way (eg. I must be in City X on Saturday night to catch a big game). You’d do everything to meet the milestones, but lets face it things might go wrong!
So plan everything in as much detail as possible, but expect to be diverted along the way sometimes. Try to have a plan ‘B’ and a plan ‘C’, and then just be flexible.
Hope that makes some kinda sense!!