Some memories are pushed deep below into your mind, to the point where you don't remember them anymore. And when they come up, you don't remember why they're there. These memories can bring up the emotions they could if you did remember what they were from, but you don't remember much anymore.
Note: This memory is from the future, but also from the past...? I don't know. Soul Reaper can see things from the future I guess, but this is also from their past... It's an amalgam of sorts - a paradox, if you will. Here's a hint: Did Soul reaper happen to lose anything before the Grim Reaper revived them as un undead reaper?