Like anything that requires mastery, sales is one of them. Sales as a skill is certainly not something you're born with.
It's an art - art of understanding behavior, art of emotional neutrality and art of communication.
Nobody is born being an elite closer. But doing reps and reps can get you there. Always picture yourself training as though you're an athlete. You've practiced and trained so many times that when you're finally in the game - it's effortless.
Keep training like each call is your next match. I guarantee this is how you'll score every time.