how can I look at life like it was before?

My best friend passed away five years ago. I've been out with other friends clubbing, going out but it just doesn't feel the same as when I was with my best friend. We did everything together, we shared memories, ups and downs and I don't think I could share that with anyone other than herself. My birthday is coming up next week, I'm thinking of going out with friends but I know it's not going to be as good because she's not there. She always organises great parties for me and I always do the same for her. I've gotten help for my depression and I'm feeling better, haven't had any downs in the past year but now I can't seem to enjoy life without her. How can I get pass that?