13MO dropping things

🐘🐘🐘 • 👧🏼 born 1/19/16. 👼🏼 lost 9/15/17. 👼🏼 lost 11/26/17.
My daughter just lets anything in her hands go whenever she pleases. It might sound like nbd but she's dropped her sippy cups full of water, books, bowls, you name it on my toes/feet and it's fucking painful. The other day I lost it and shouted at her and I feel so guilty because she got scared and cried. Does anyone know what I can do to get her to stop? Will she grow out of it? Is this normal?