One of the things we say to our sponsor mids as they get anxious about something coming up, instead of saying "you'll be ok," is:
Remember how you felt the night before I-Day? Did you handle Plebe Summer? Yes, you did. These feelings are normal, and as soon as you get into New and Scary Thing X, you will be in it, and you will get through it.
As time goes on, they realize: First academic semester? Usual apprehension, get into it, survive it. First semester exams? Ditto. First flight school hop? Ditto. First week at TBS at Quantico? Ditto. Night before reporting to first ship? Ditto. Night before first carrier qual attempt? Ditto. Night before any combat operation in any combat zone? Ditto. Night before your oral warfare board? Ditto. Night before first day as XO? Ditto. Night before Change of Command as incoming CO? Ditto.
Our mids are surprised and pleased when DH and I share our own stories of apprehension before major events as a normal thing. Once you self-check and say - ah - normal - once I get into X, I can get through it - the pressure eases.
What is it that Louis Zamperini said in "Unbroken?"
"If I can take it, I can make it."
Edit: One of the things I realized after a while is that the Navy gave me stretch assignments, asking me for a bit more each time. When I was an Ensign, I thought no way could I be a CO one day with that much responsibility, people, dollars, stuff, schedule. The Navy started me off with 65 sailors on 4 tugboat crews. Some years later, they really ramped me up (multiple oh crap sleepless nights leading up to it) as the XO of an intermediate ship repair activity (SIMA) with over 900 sailors, big complex, big budget, high-pressure schedule, as a Lieutenant Commander. By then, though, I knew how to talk myself down and put on the game face. Of course, once you feel comfortable and competent in the role, time for another stretch. Most days as a CO, behind my positive and confident game face, I alternated among OMG, Whee, oh no, Yessss, what?! and They Are Paying Me To Do This.