I found peace by understanding the choices my son would make through his sickness were going to be generally sick ones for as long as he drank and would ultimately damage him for whatever remained of his probably very short lifetime. The idea that I could influence that in the least bit from afar I understood was a ridiculous fantasy, and I'm not one to value ridiculous fantasies highly.
If they are sick then they are sick, even if we would much prefer they were not sick. Wishing their condition away and expecting that to have the least affect is by general consensus not a worthwhile effort to make. It implies we somehow have a power to influence what they cannot themselves influence.
Controlling the uncontrollable twice removed isn't a bet I would place anything on. Much the same as if he'd like to fly and my feeling if I wanted him to fly hard enough then he would soar up into the sky.
How reasonable would it be for me to get obsessed with him continuing to walk instead of flying around like a little bird and make myself suffer constantly that he must instead always and forever deal with gravity?
My son may get drunk again after staying sober 10 years now. Alcoholism isn't cured, and remains a constant condition throughout an alcoholic's life. I could get that and bemoan it, or I could just simply get that. Bemoaning it serves zero purpose that I can see.
If I don't drink I'll be 30 years sober in a few weeks. While alive my parents saw me take care of my condition and eventually worried so little about relapse that they on many occasions offered me drinks. They didn't understand what I know and didn't need to, they just took it for granted my sobriety would be permanent and forgot all about it.
I loved that I was able to remove my problem from their concern. Your grandson has a problem that is his business to correct. You can hope that he does that for his benefit, but your involvement in his problem ends there.