How do I manage the impending grief ?

Good evening.
To sum it up, I'm extremely attached to my mother, and I greatly fear her passing.
I can't even imagine it. Had anyone been through the situation I'm in ? How did you manage ?
Thank you.

I always feared my mother passing some day and last july it became a reality. In December 2014 she became unwell and tests confirmed my worst fears.She was diagnosed with lung cancer that had spread to her liver, pancreas, spine,and eventually her brain. She did chemo but it did nothing. I slowly watched the woman who was my everything and only friend in this world,who I loved with every fiber of my being die. I looked after her and gave her her wish to die at home.it's been 7months and I feel like dying everyday and just on the weekend I suffered a heart attack and wish I had died.I'm 41 have no husband or kids or friends. I can't wait to join her.
Sorry this is depressing but cherish every moment you have as if it were your last with her,because you never know what's around the corner. I would not wish this on my worst enemy ,this emptiness I now carry around every second of every day.

I know this post is somewhat old, and this may come too late, I hope not. I empathize with how you feel, with me it's my dad gone 8 years now. i loved him very much, he was the one there for me at the end of the day in my childhood. I still miss him in ways that are hard to describe. He was an aviation enthusiast and flew his own his plane, flying was a joy in his life. Every time I hear a small plane flying overhead, I get teared up knowing how much he loved flying. But he didn't hold a lot of regrets or grudges in his life, he said life's too short for that business so enjoy what you do have. That's a life lesson I learned from him.

Cherish the moments you have with her. Appreciate what your mom gave you, it's the positive way to pay forward what you learned from her.