That sucks man. When my last cat died I cried like a 4 year old girl for 2 days. He was my friend. Pets, even fish, ask for nothing, and give unconditional love. Just remember, "he's not really dead, as long as we remember him"
Wait a few weeks, cycle maybe 75% of your water, and then get fish 2.0, and pretend like the last fish was the new fish's brother.