This is the first warning sign of the development of alcoholism/addiction. The same Pleasurable feeling obtained earlier with one or two drinks /uses is not reached with the same quantity of usage .More of the substance is needed to get the same feeling. Eg. A patient told me “I started drinking at home and realized I needed more alcohol to get the same high as earlier”
This is not going unconscious or falling flat. During a black out, one may go through many activities like walking, talking, even driving a vehicle ‘apparently normally’, but have NO recollection of them afterwards.