When we speak in front of people, sometimes we get so caught up with ourselves, or we're in such a hurry to get it over with, that we forget to control our breathing.
There are lots of different breathing techniques that can help both before and during your speech. Former opera singer Allison Shapira wrote in the Harvard Business Review that breathing is key to persuasive public speaking and recommends breathing deeply, then speaking "on the breath", using a deep outward breath to support your words.