Maria Shriver to World -- Read My CHEST!!

Maria Shriver and a friend fired off some advice -- possibly to Arnold Schwarzenegger -- during a stroll in L.A. today ... courtesy of their not-so deep tees.

Shriver's top said, "Change the world with your courage, wisdom and strength" -- while her friend sported the less wordy ... yet equally preachy,  "Karma."

Total coincidence.