You just used a quote from the Confucian Analects, in the section called the Great Learning. Many English translations of the Confucian Analects have been done. Here is a quote from an older translation that corresponds to the quote from the original Chinese that you used: "If you can purify yourself a single day, do so every day. Let no day pass without purification!"

It's an old Chinese saying. It is a saying that encourage a person to keep improving and be advance. Direct translation: [if-day-new, day-day-new, again-day-new] If (you) make new progress daily, (then you are) new everyday, (don't stop and) make new progress again.

If we can use new to replace the old, every day you must to use the new instead of the old, every day uninterrupted instead instead.