“If you do what you’ve always done, you’ll get what you’ve always gotten.”
Attributed to Tony Robbins (in this exact formulation) and many others in similar words on the Internet (for instance “Do what you have always done and you’ll get what you have always got” sourced to Sue Knight) - I have no idea who first said it or in what words. But a very large number of people have demonstrated its truth in practice... including me. Dang.