[ftio]

As a person who fits your description above, I can attest that at least for me: it is 100% preparation.

For big presentations, I put in practice time equivalent to 10-20x the time of the talk. For a one hour presentation, I'll practice for 10 hours at least, if not substantially more.

For high-stakes conversations with Important People, I think to myself, in advance: what do I want to achieve from this conversation? What do I need to say or ask in order to achieve those things? This is true even if the conversation is "just a chat." The goal might be as simple as: build credibility and familiarity with Important Person. Pro tip: plan up front what you're going to ask/say if there's awkward silence. It happens even to the best conversationalists. Better to be prepared than to be caught flat footed.