Watch out, this defies conventional wisdom: If you're about to decide about something complex, you will do better if you don't exhaustively research it.
In this case better means both objectively better results and more happiness for less effort.
There's an overwhelming amount of information out there. For simple things, it's possible to think through the decision completely, but complex decisions will certainly tempt you to doing extensive analysis in order to do the best you can.
Whether that analysis is warranted depends on your objectives. The assumption here is that you want to meet your needs and be happy with the result.
If you'd rather not be happy with the result, feel free to analyze it to death, but be aware that diminishing and sometimes even negative returns kick in on the analysis, and you are ruining your chance to be happy with the outcome.
It's a waste of time to try to process it all. Trying to figure it all out is certainly time consuming.
Functional MRI studies show that the dorsolateral prefrontal cortex, the part of your brain that makes good decisions, shuts down when problems get too complex. If you try to juggle too many factors your frustration and anxiety will rule and you'll make worse decisions, or fail to decide at all.
In terms of your happiness, the more thought you put into it may get you a better result (subject to the frustration and anxiety we've already talked about) but you also get to know about all the ways you might have been able to do better.
For more info on this, refer to Sharon Begley's article "I Can't Think" in Newsweek, March 7, 2011, and the TED talks from Dan Gilbert: "Why are we happy? Why aren't we happy?" and "The Paradox of Choice" by Barry Schwartz.
You'll be happier with your jeans, your movie selection, or the house you buy if you consider only a few than if you try to look at all the options and then drive yourself nuts thinking about what you didn't get.
You did want to be happy, right?
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