Sly, if you want to honor the memory of your grandmother, start getting your life together, start working out, and throw away the "it's too late for me" crap that you seem famous for in these forums out the window.
My life changed when I lost my dog, this might be the loss you need to begin your new life. As much as I loved my dog, losing him really jumpstarted my life and got me out of the mire I fell in. If you continue life, when she is gone, with a defeatist mindset then you will certainly be dishonoring her memory.
I never had a connection with my grandmother, or my mother for the matter. I have a physical mother but we never talk, knowing a mother is virtually unknown to me. Consider this as a great leverage you have in having a grandmother you were close with, now use that leverage to gain momentum and purpose in life. Find a purpose outside of romance and outside of videogames, something more divine than the vanity that's in the world. And use the promise of reuniting with your grandmother in heaven as fuel to motivate yourself to do good in the world. Find a sense of duty. Men with a sense of duty can't be stopped, they're a wrecking ball that's just blasting through the walls in the maze of life in pursuit of the goal. But to become that you need to manage well the small details in life, for me, it started with working out each day, which then dovetailed into bigger goals and a stronger ambition.
But take time to mourn when she's gone, but you best not let yourself go, you would be shaming her memory if you did, and all the attention she gave to you would have been for nothing.