Work related post ahead.
It is not easy explaining these principles to people who want to see a detailed six month GANTT chart that takes six weeks to create and six days to undo. If you spend six weeks actually doing the work, you'll be six weeks closer to the goal and six weeks wiser.
The dude with a GANTT chart just has a GANTT chart.
One of our investors has a great analogy about choosing between being a bus or a heat-seeking missile. The bus has a route, a destination, and an itinerary that it must stick to. The heat-seeking missile is built to adjust. You fire it in the general direction then iterate and evaluate as you move forward. Hit the thing that's hot, even if it moves (and it will move).
I'll leave you with a Winer-ism I like a lot from 1995 called We Make Shitty Software…With Bugs! It's just the first four paragraphs (pre-permalink era?) so don't worry about seeing the phrase "Indigo Girls" on that page.