The best way to explain this is to think about your brain like it's a computer. Which in many ways it is. Research out of the University of Toronto shows remembering the "Big Picture" not the small details is good for your brain over time.
The hippocampus is where our brain stores memories. The research show this part of our brain actually filters out less important details so we can remember more critical information. It actually does it's own clean sweep to get rid of old details to make room for new stuff.
Plus, now that we have Google our memory doesn't have to waste space remembering phone numbers, addresses or how to spell things. At the rate I forget things this is really good news!