When my wife and I were new parents, it took an hour to pack and prepare for a short excursion to the grocery store. We would have a humongous bag of things ready "just in case" - diapers, two kinds of wipes, a change of "onesies", blanket, bottles, forumula, baby powder, chalk, belt, chains... oops, off topic. Anyway,
now we look back on all of that overpreparation and laugh. It's a wonder we got out the door AT ALL and, as you might expect, we didn't go out much.
Planning and reflection are crucial but there must be doing to give planning and reflection purpose. Planning & reflection lead to doing, which leads to more reflection & planning, which precedes more doing. Without doing, there is no purpose to planning or reflection.
Here's how it applies to strength and conditioning: Most journeys and training efforts are not epic quests, just short 1-2 hour trips. Don't spend needless hours and days planning out complicated splits or periodization schemes to go the local gym and bench 135. Just do it.