Having a difficult time getting over a busted friendship?

I've had those before, and it usually takes me a couple of months and I'm like "out of sight, out of mind" ... but with this particular friendship bust-up it has been over a year and I still miss them like crazy (he's male, I'm female, and our friendship was platonic and lasted several years). Last night, I had a dream that he was bouncing on a trampoline and I was bouncing on a trampoline next to him and he never said hello. I think that dream told me something, don't you? Regardless, why is this taking so long to get over?