When you make the same mistake again and again, would you describe your behavior as something that happens continuously or continually? These terms, along with their adjective forms continual and continuous, are often used interchangeably in speech and writing, obviously because they both come from the verb continue. But style guides urge writers to practice discernment when using continually and continuously.
Continually should be used to mean “very often; at regular or frequent intervals,” and continuously to mean “unceasingly; constantly; without interruption,” especially in formal contexts. To put this into context: reading grammar blogs continually (at regular intervals) throughout the day might be a fun way to boost your knowledge about the English language, but doing so continuously (without stopping) for the duration of a day would likely result in fatigue, hunger, and—dare I say—boredom.
Despite the rules of good usage outlined above, it is common for continually to be listed as a synonym for continuously in dictionaries, or for them to be used interchangeably in the wild. So how do we maintain the distinction between them? One way to remember the difference is to use the letters in each term as a hint: continuously has an uninterrupted chain of Os and Us toward the end, reminding us that it means “uninterruptedly” or “unceasingly.” Continually, is interrupted by two jutting Ls, reminding us this term is associated with breaks, interruptions, and intervals.
Knowing the difference between these terms will give you an advantage in formal settings, but don’t worry too much if you can’t keep the two words distinct all the time. After all, style guides are continually published, but the language is continuously changing.