Health isn't all or nothing. You can take baby steps. If you eat crap, that doesn't mean you've "failed" and that you might as well continue to eat crap for the rest of your life. You'll s*** that stuff out the next day anyway. Just aim to do better next time.
Your body gives you plenty of chances to do better. It's never too late! Something is always better than nothing. If I have to start back from scratch, so be it.
Just Do It!