The reason why you have memory is not  just to remember the past, describe your objective world and wallow in misery as it may be.

the reason why you have memories is so that if similar something bad or good that happened in the past wants to show up in the present, you could figure how best to handle it with alacrity as much as possible.

 For the bad memories, you make sure they doesn't happen again.
For good memories, you make sure that you replicate it.