I thought he could have gotten his shit together before the Picard meeting. It's not like it was sprung on him. And it's not like everyone wasn't very aware of how assimilation takes you over completely. Heck this is space, the old "alien eradicates my individuality and uses me as a meat puppet" story is hardly something new.
And can we say IRONY! Because this happened to Sisko's OWN MOTHER!
I wonder if he thought of Picard when he found out the details of that.
(And no, I never disliked Sisko because of that. I thought he walked damn weird in Season 1 and I never like his "ahhh HEEHEEHEE" laugh AT ALL but that's about it.)