In at least some of these cases there's a likely asymmetry between the two Sides of the Chair, which may make it harder to maintain that we shouldn't favour one side's preferences over the other's. Namely, in some cases one of the two states is not sustainable. For instance, it's impossible and/or impractical to be high on (say) heroin for more than a smallish fraction of your life. (I think that's true, but I am not a drug expert. If it happens not to be true about heroin, that probably just means I picked a bad example. [EDIT: as David Nelson points out, that was in fact a bad example, but replacing heroin with hallucinogens fixes it. END OF EDIT]) So doing something that gratifies you-while-high but more severely harms you-while-not-high is likely to be bad for you-on-average.

In some other cases, one state is indefinitely sustainable but only at a cost that both versions might (if they could be convinced that the cost is real) find unacceptable. For instance, one can doubtless stay crazy for ever, but if one could explain to crazy-you that taking the antipsychotic drugs at least most of the time will make it possible to have a job, a partner-of-the-appropriate-sex, a life that doesn't involve being locked up all the time, etc., then I suspect that even crazy-you might agree that the price is worth paying. (Of course, if crazy-you is crazy enough then this is a hopeless project. Too bad; can't win 'em all.) Or: even when you're guzzling chocolate cake, you might well agree that you have to moderate your appetite most of the time because even cake-guzzling-you doesn't want to be a ball of lard six feet in diameter.

I don't claim that this asymmetry makes it obviously definitely right to enforce the wishes of you-in-the-sustainable-state even when you're in the unsustainable state and have very different wishes; but it does seem to offer a better justification for doing so than "simple bias in favour of mental states similar to our own". In some cases, at least.