"But you are deciding what I should do ..." Hmm.
I think your intention here is a good one: "what's sauce for the goose ...", "Universalise maxims ...", "do unto others as ..." are individually useful tenets in moral argument. (They express something essential to right-and-wrong.) But something doesn't quite sit right, does it? Are you really being even-handed? Let's see.
It's sometimes useful to look at argument structure if we want to see the ethical wood as well as the moral trees. I suggest we try here.
Suppose A says, "My autonomy entails you shouldn't stop me doing X to myself"; suppose B rejoins, "My autonomy entails I should be able to stop you doing X to yourself." (A: me; B: you.)
OK, now try to universalise. A is OK; no obvious structural difficulties there: "for every P and Q, P's autonomy entails Q shouldn't stop P doing X to P".
Try B: "for every P and Q, P's autonomy entails P should be able to stop Q doing X to Q". This is problematic, since stopping someone doing something denies that person's autonomy, doesn't it? (That's what autonomy is, you might say.) So B is making two contradictory claims: that everybody should have his or her autonomy respected, and that everybody can have their autonomy denied.
B's rejoinder can't stand as a moral principle - it could not be true, because when universalised it both asserts and denies a person's right to have her/his autonomy respected. Do you see, @Grammarnut?
In short, you are mistaken.
As for society or the state arrogating to itself decisions of life and death (and this includes eugenics), this is a straw man here. No-one is saying (certainly I am not saying) the state should decide whose life is valuable or worthless.
We all agree there need to be safeguards. Of course we do. (Which makes many of the arguments put here and elsewhere on this matter simply insulting.) But this should not - does not, cannot - override my autonomy, and hence my choice, as a basic moral principle deciding matters of my own life and my own death.