While it may be counterproductive to dwell on the past too much, memory certainly has its uses. If not specific memories, then certainly the massive subconscious recording of all we experience shapes our behavior.
But human memory is not at all like computer memory: where computers record only exact data, and retrieve it perfectly if no hardware or software error corrupts it, the human mind is not as directly accessible at times: where we may remember songs we heard before word for word after many years because of the repetitive patterns of music that accompany them, singular events often escape retrieval.
Oddly enough, the subconscious can help when all else fails: if something is on the tip of your tongue, it may not be easy to just spit it out, but stop focusing on it, and within minutes or even seconds the answer arrives again!