I was driving my 2002 Mitsubishi gallant and the transmission just gave out

Hello, That sounds very frustrating, and hopefully it is a simple fix like low transmission fluid or a leak into the main harness connector for the transmission. I hate to say it, but automatic transmissions are very complex, and I avoid offering speculation when there is automatic transmission failure because there are so many variables. In short, the best thing you can do is ensure the transmission fluid is full, not over or underfilled, and check your fuse for the transmission control module. If no luck there, it needs to be diagnosed by a professional.