Maybe eat as normal (but eat well) and look into remedies to aid with nausea. I heard lemon balm tea helps, although I'm sure there is a myriad of different tricks.
Also keep in mind that a certain level of nausea is inevitable with psychedelics, and though I've never purged (even with heavy brews like mimosa tea) I'm always prepared for the possibility. Long live the yak bucket!
I don't want comfort. I want God, I want poetry, I want real danger, I want freedom, I want goodness. I want a clever signature.