Maybe you can make a scrapbook about them if you think it would help? Get pictures and other things that remind you of the person, maybe even write a poem or a story about them (even if you don't normally write, it'll make you feel better). Write little scraps that you can stick in about days out that you went on with them, funny things they used to say or do etc. It's a real project that you can throw yourself into, it'll make you feel better and bring out the positives of the person that you lost and what you gained from knowing them. Then if there's anyone around that you can show it to and talk about it with, that'll help you too.