Ask HN: How do I break the habit of architecting/engineering too early?

It happens all the time. I get to thinking about an idea. How simple it is and how it deserves my immediate attention. From there on it grows like one of those "Just add water!" sponge things.

I start to think about the market, audience, user. I start to think about potential features, how they'll fit in. How usable it will be to the power users. Then, how the non-power users will cope with it. How it will be understood for a first time user. What's redundant, what's necessary. Is my wording correct? Am I addressing the user like an idiot?

Besides having my friends sit over my shoulder and smack me in the head whenever I wander off course, what suggestions do you have for me?

I am totally committed to breaking these habits, if only I knew how.