It is strange the way that we associate music with memories.
It is like a strong perfume that is impossible to disassociate with an era.
There are songs I cannot listen to because I was sad during the month it was in my playlist, or even because I feel that I have moved on from that time period. I now listen to a song knowing that one day, likely very soon, I will have grown out of this small era and will associate the song with the general mood of the month.
Small things in life change rapidly, including the clothes you choose, the breakfast you eat, your daily routine, the people you talk to, and the music you hear. Listening to music from a different era of mine often makes me feel uncomfortable, even if it was a good era, simply because I am not there anymore. It reminds me that times have changed, even if it is month to month.
Sometimes I regret listening to the same four songs day after day on my drive to school because I know what I am building. It will be a memory for my future self to listen to and reflect.
The automatic association of music and memories is hard to shake. They are not implicit memories, it is the general tone of the era that went unrecognized until you hear the songs and realize the moment has passed.