Xanx for flight

My doctor prescribed me 0.25 mg of Xanax for my flight. She advised me to try it before my trip to see how it affects me. I'm really afraid to take it. She mentioned that I could take half of the pill. I weigh 110 pounds, and I don’t want to feel groggy; I just want to feel calm. I've taken propranolol before. Will Xanax just help me feel normal without anxiety, maybe making me a little sleepy?will it feel like I’m just on propranolol, but without the mental anxiety ?