Engineering
Customer demos will expose what your roadmap got wrong. The hard part isn't changing the plan. It's communicating the change without losing your team's trust.
You can always add signals later for specific decoupling needs. You can't easily remove them once they're load-bearing. Here's what that costs at scale, and how to design for both paths from the start.
Why the best engineers struggle most with shipping imperfect code, and how to build the instinct for when good enough actually is.