There exists a theory to the effect that we never actually forget anything: we merely misplace it. It goes something like this:
Near as I can figure, it only gets “lost” because we stop keeping track of it. There’s so much knowledge stored in that vast, disorganized warehouse of knowledge both useful and not, that the only way to get hold of any one piece of it when you want it is to keep the index up and running. But the way the brain works, the index consists of associations rather than actual location addresses like on, say, a computer hard drive.
Which is why when I’m trying to remember something and having trouble, I usually have to go back through what I was thinking about when the information got filed. Other times I may just have to give up and wait for something else to accidentally spark an association (which often happens just about the time I stop trying to remember it).
For a highly-unreliable system, this is actually pretty reliable. If there’s something I need to do tomorrow, I don’t write a note to myself; I leave something out of place. The next day, when I happen upon the anomaly, the connection is made.
I might also suggest that this propensity is of particular value to the blogger. There’s no way I can recall on demand the contents of the last 15,000 posts (which would go back to the fall of ’02 or so). But if something current happens to match up with something I once said, there’s the accidental spark, and the words will start to flow. You thought I was quoting myself for the sake of search-engine standings? No, just rebuilding my own internal not-really-an-index.
There’s one further complication, at least regarding my own memories: certain of them are tagged as Bad, things I’d just as soon not think about at all, and if one of them happens to be activated, the whole lot can come crashing down on me at once. Under those circumstances, the best I can do is to invoke the Scarlett O’Hara Temporal Displacement Method.