I messed up! I changed my keystore and Google Play won't let me update my app, now.

I know I really screwed up, but I need help. Here’s what happened.

I made a keystore at first with a password that I could easily remember but that was really insecure so I decided to make a new one (I know! Stupid!) and the default name was just something like user.keystore so I when I was saving, I overwrote my old one and I have no idea how to get it back. I have old builds on the Play Store and my computer. Is there any way to get my old keystore back? Please help me!!!

Nothing. There is nothing to be done. The app needs to be resubmitted as a new app and all previous users will have to get the new one.