They are speaking from experience, some of the methods to enjoy and control their drinking that they tried and failed at.
In essence they are saying...'we proved to ourselves we couldn't moderate our drinking, but we are not trying to pronounce that as impossible for the entirety of humanity and that there may be someone out there who can, and if they can do that and are successful then whoopiedo for them, but it still doesn't change how things for us and everyone we know.'
Hope that helps make that passage more clear to you.