Merrion recalled a time when he was in Quen's shoes, struggling to make the spells come out the way they were supposed to and having had little luck. Calm down, they had said, and concentrate. Quen didn't seem to have trouble with the latter bit, and Merrion was almost inclined to think that she was overthinking it, something else that had befallen him when he was younger and something he still had to fight when learning new spells.
But if she was nervous, that meant she was scared, and that meant doubt. "Be more confident," he offered. "Try imagining yourself doing the spell perfectly before you cast. Don't think about what might go wrong. Think about it going right."