Locked Out

For some reason my login password is not working. I am trying the same password that I've been using the last 4 years and all of a sudden its not working. Sounds like user error here but I know for sure I am using the same password, no capslock or any special differences... Is there a way to reset the password from the guest account? or anything? I've been using the guest account for about a week now and I am losing it haha.... HELP Please!