In my lifetime I've had to plan, design, and produce everything from machines for manufacturing lines to residential hvac systems to decks to musical scores...oh, and computer programs too.

And your observation about this question being applicable to many areas of creative endeavor is very true.

In every case there is an optimal medium to achieve. At some point planning, calculating, goes beyond the accuracy required by the job and you are wasting time. At the same time, diving head first without a minimum of planning leaves you open to pitfalls.

You can buy very complicated heating ventilation design programs. After you spend a week getting the dimensions and r-values of everything in your house, then another week inputting the information, it will tell you what diameter your heating ducts should be for ideal air flow. In the meantime, an experienced hvac guy measures the length of runs, and sketches the main trunks and branches. Counts a rough number of elbows needed. Then, with that reasonable planning done, goes to the hardware store to buy the ducts, the elbows, and a few boxes of screws and duct tape. He'll return what he has extra. He's done while you're still measuring, and the difference in system performance is insignificant.

At the other extreme, the guy down the road set to building his new house with no planning (really). All went well until he discovered the new by-laws on septic systems and his half-finished house sat there for a year while he figured out how he would achieve compliance with property-line set-backs. A minimum of planning would have spared him this major pitfall.

General rule - do a reasonable amount of planning. Of course, what is reasonable is very subjective, and that's where experience and skill comes into any profession. Experience and skill at estimating what is a reasonable amount of planning comes with, you guessed it, experience - that is, mistakes.