My mind is tangled for a stupid reason, but it bugs me

I was just pulled over about 15 minutes ago. My first even encounter with the law. I don't feel too guilty, as I didn't break any laws intentionally (missing year sticker on my plate, which I had EVIDENCE that it was once there). No ticket, not even a warning, just a "get that done ASAP" and that was it. But I'm stressed, and annoyed and frustrated. I KNOW I had proof of insurance, I just couldn't find it (the officer could, so all was well), I was 500 yards from my house, and this was my good karma for remembering my friends birthday. I could've waited until the morning and avoided it all, but now it's all I can think about. Why me? My driving was immaculate (because of the officers presence) and there are violent crimes happening as we speak. But no, 1 missing sticker on a clean car. Evil.