It's of course possible to be wrong in either direction -- this difference matters though i think it doesn't and vice versa -- but in general, we tend to be pretty good about taking seriously the things that really are serious, but pretty bad at not wasting time on things that don't matter much. This shows up in the paradox of choice, but really just imagine someone hemming and hawing over two brands of cereal in the aisle at Trader Joe's and you get the picture.
So the practical problem isn't really "how do you know until you analyze," because we more often fall into opposite the trap and waste time systematically attempting to optimize choices where there is little value to be gained. We should step back in more cases and remind ourselves that most differences make no difference at all. Save your time and energy for the ones that do.
Big decisions are often like icebergs. Most of the important stuff is hidden below the surface. No matter how much you analyze the tip you still have an essentially 50% chance of getting the decision wrong. It's really hard to make a major decision knowing that you have a 50% chance of getting the decision wrong, but over-analyzing the tip of the iceberg is not going to improve your decision making.
There are a lot of insightful heuristics from decision making that can make big decisions much better/easier/etc.
I don't think people would spend any more time on big decisions if they made faster/fewer decisions with little "value" to gain, if anything I think their habit of making fast decisions would mean they spend less time/worse on the big ones!
And no doubt that sometimes it's just nice and pleasurable and interesting to deliberate over anything at all, making small things grand, but it's also good to know when it's actually optional.