I'll leave this here: http://marshmallowchallenge.com/TED_Talk.html
There's a big difference between correct planning and too much planning and I wish I could point out the big glaring wall that divides the two. The honest answer is that I don't know until I've walked in your shoes.
Most startups always go with : Idea > Platform > Tinkering > Launch
Between Idea and Tinkering is a feedback loop with improvements. But most importantly, there has to be someone outside the loop to tell you when too much planning is going on. When you're in it, you don't see it.
The loop you talk about is known among Lean Startup people as the build-measure-learn loop: http://lean.st/principles/build-measure-learn
The folks I see doing best are the ones with a clear vision who iterate as frequently as possible, testing their assumptions in order of risk. The right amount of planning is the smallest amount to let them learn frequently.