Im sorry but I have to disagree here. just because you and your internal system were able to take these preventative measures does not mean everyone with DID in your words "He should be able to do the same."

not every one with DID has control over what their alters can and cant do..

example I had no control over what my alters did and didnt do. my alters were so categorical (other locations use terms like "compartmentalized" "definite" "Marked" "separated" "behind the wall" the DSM uses the term "distinct") that I had absolutely no control over what my alters wore, said, did, thought, ate, or even how they behaved. my alters all had their own way of being, their own reason for being, their own job....

for me and my alters there was no such thing as ok Angry one you are not to do this and this, or ok Rainy you cant cry anymore unless you are in this room or that room, there was no ok Sunny no laughing in the car, you can only laugh when we are at home in the bedroom....

most of the DID people that I know in my personal life and through my job, do not have the kind of control over their alters where they tell their alters what to do and what not to do.

it takes a heck of a lot of coconsiousness and many many yrs of therapy to develop that level of trust and communication with alters for most DID people I know,

for me the only thing that stopped my alters from acting out, doing things I did not approve of was their integration where we all became one person again. now there are no alters acting out because there is just me and everything they were became me.

my point is everyones internal system of alters is different, just because one person can control what their alters say and do does not mean everyone who has DID has that ability.