My predecessor sent me a message: If I drink too much, I will lose my mind. How should I reply?

I don't think it's necessary to reply at all, just pretend I didn't see it. Because you don't know what to say. If he drinks too much, then he may not remember anything. So maybe it will make her unhappy. Or a sad past reminds her. Now that you have broken up and don't want to get back together, there is no need to go back.