Balancing between over preparing and under preparing

Balancing between over preparing and under preparing Hey guys, I have a problem that I am unable to figure out how to navigate. At work during calls when I have to give a presentation or lead a meeting for instance, I often struggle with under preparing vs over preparing. If I under prepare I feel less confident about what I know which causes nervousness that exasperates the stammering. If I over prepare with exact words that I need to say (in case I write it down beforehand) I place too much emphasis on saying what I need to say accurately. It comes off as forceful and I end up stammering a lot more. In casual conversation I don't stammer as much because I am more of a flow state. How do I replicate that when I have to give a longer speech, lead a call or something similar. How do I balance over preparing vs under preparing. Thanks