Is that childish???

I guess it depends ...

It depends on whether being told I can't do something means it's doubtful I have the ability to do it ...or whether it's forbidden for me to do it.  

Is forbidden too strong a word??

Should I say ...it's perhaps not healthy for me to do??

I do have the ability to choose ...and I have the ability to choose not to succumb to the temptations of the things I should resist??