After a full day at the office you get into your car to drive home. This is an excellent moment to reflect, so you try to get a good picture of the day. Strangely enough this is not easy, and some parts of the day seem to have disappeared completely. How is this possible ?
You don’t have to worry, there is nothing wrong with your memory. However, there is something wrong with the way we think our memory works. Most of us think that our memory can be compared with the data storage devices on our computer. That it records exactly what happens, and if I need information, there is a wonderful mechanism to pick up the data exactly as stored. This is not the case.
Firstly, the way in which data is stored is not a factual recording, nor will it remain the same over time. Only recently did we discover that even the process of recalling memories changes that same piece of memory. So our memory is by definition not reliable.
Secondly, our memory is selective what to save. There was no evolutionary advantage of storing as much as possible. That is why our brains only memorise what is relevant, what could be useful in the future. Stepping outside of the cave and hurting your toe on a rock is relevant and will be recorded in your memory. A fairly normal day in the office without special events will be quickly forgotten, or not even registered.
This is the reason why, when you drive home from the office, you have such a hard time to remember what happened that day. Even if it was a very busy and productive day. However, if you have spilled coffee on your new pants, you will certainly remember it.