OP, I had the same kind of relationship with my mother. She was my best friend, my confidante. When I was upset or stressed she knew how to change my way of thinking so I could look on the brighter side.
Then she was diagnosed with terminal cancer. She had chemo and fought hard, but sadly succumbed 4 months later. Only the night before I'd had a conversation with her by phone. 12 hours later she took a heart attack and died.
It was so, so hard living without her. When I'd hear or see something interesting, I'd say to myself "Oh, i must tell mum" then realise she wasn't there.
She died 5 years ago and I still miss her terribly, but I live in a small town where everybody remembers her and loved her and it does me good to talk about her. You just learn to live around the big loss. Even guys tell me how my loss (I actually lost both my mother and father to cancer within 4 weeks of each other - I'm only talikng about my mother here because it relates to OP, but I adored my dad just as much) has made them appreciate and love their own parents more. That makes me smile!
It is so normal, OP, and just enjoy it. (I hope you don't think I'm being morbid.)