Two things that genuinely help — knowing how invisible your nerves are, and treating a racing heart as readiness rather than malfunction — plus a breathing routine short enough to run in a corridor.
Trying to suppress arousal mostly increases how much you notice it. Reinterpreting the same racing heart as your body getting ready performs measurably better than fighting it, and takes no effort.
Speakers substantially overestimate how visible their nervousness is — and being told this has been shown to reduce anxiety and improve delivery. It's the cheapest intervention available and almost nobody is given it.
Power posing didn't hold up — one of its own authors withdrew support. Nor did smiling-to-feel-safe. This toolkit leaves both out rather than passing on things that sound good and don't work.
Losing your place in cue cards is a two-second pause. Losing it mid-memorised-script is the thing you were afraid of. The fix for forgetting is structural, not psychological.