My Best Friend Is Gone

What is it about certain songs, certain pictures, or even cars, television shows, billboard signs, etc. that can just flood your heart with emotions? I don't understand why I can look directly at a picture of someone or even talk directly to them and not feel anything, but when I hear a certain song or even someone else says just the right thing, I can feel myself fill up with an incomprehensible amount of emotions. Is it just that we get so used to looking at something that it stops stirring up our insides so the things that actually do surprise us? Or have we all just tried to become numb to the continuous pain that keeps attacking our lives. At some point I guess the anesthesia has to wear off and that's when those sneak attacks from songs & pictures & cars arise. I'm not really sure which of the two it is... maybe it's a little bit of both. I sit and I look at a picture of him that's on my wall every night before I go to bed. It stopped stirring anything up inside me months ago. I think about him every day and I miss him immensely, but I can't remember the last time I cried about him not being here. It's not because I don't want to; it's more so because I just haven't been able to lately. So maybe I have gotten used to my surroundings, but I think I've managed to numb some part of myself as well.
Whatever the case may be, healing is a process and, in this particular case, a very long process.