Your automatic (unit, functional, system) tests assure stuff doesn't break (too much), and manual QA happens after deploying. If something is broken, you can fi

Your automatic (unit, functional, system) tests assure stuff doesn't break (too much), and manual QA happens after deploying. If something is broken, you can fix it very fast, since you are deploying continuously. Stuff might sometimes be broken on production, but you could argue this makes people think twice before pushing to master. Also, you can deploy to production with a delay (e.g. 1h) and deploy to a QA server first to give the QA people some time to check before stuff goes to production.