I'm sure the brain has to do this every so often just to keep us functioning, but the funny thing is as people get older it is childhood memories that come back instead of what happened last week.
I think what happens is that while you are young you have all this spare memory, so your brain stores stuff, but as you get older and the RAM fills up your brain has to be more selective. Once you get to my age the brain thinks "I could do with an external drive", so it doesn't bother to store what you had for breakfast as that would use precious memory. It only remembers important stuff. It is like when you first got that 1.5Tb hard drive you stuck all sorts on it. But as it fills up you don't always delete, you are just a bit more selective as to what you save.
All this only applies to men of course. If you are a woman you remember everything, forget nothing and never let him forget it.
