Can I legally change my mind?

I got a new car today that my fiancé really wanted me to get, but I have changed my mind and I want to give it back. I was approved by the bank and even signed all the paperwork today, but I now changed my mind on such a large commitment (5 years) and I want to give it back. Any lawyers or car dealers that know what I can do? I got it through Chevy. I’m freaking out!!