I know exactly what you mean. It's such a bittersweet feeling saying something perfectly because that means you can physically say it but for some reason our brains won't let us do it like that all the time. I especially hate when people say 'hey you didnt stutter there!' as if they're complimenting me when in reality it is so condescending and upsetting. I struggled a lot with jealousy of other people and that feeling of resentment (and awe) at how they don't even have to think about talking when it's something that's always on my mind. I don't really have any advice except to let you know you're not alone in feeling that way. I've finally gotten to a stage where I feel like I've accepted my stutter and don't let it affect my life as much as I can - but it'll never be something that I don't think about.