If you haven’t practiced you will run over. My first talk at a local meetup was supposed to be 30 minutes, I only got through half of the slides. This is solved by practice: actually rehearse the whole talk (to an empty room, then to an audience).
Peak scary is ten seconds before the talk. I didn’t anticipate it to be this scary. But once you get into your element (by talking about things you care about) the fear goes away completely, it even becomes fun. At least it did for me.
It helps if you have one idea to center your talk around. Like in Inception movie, what’s the one thing you want to put in their heads? This helps you decide what to cut (and you might have to cut things when you realize you’re running over the day before the talk).