There’s no denying the usefulness of this as a teaching. It encapsulates a principle that’s been articulated in similar words by many modern teachers of Buddhism. But the language used is completely alien to the canonical scriptures.
Fortunately I haven’t seen this on any sites that are obviously run by Buddhists. You do get a lot of professed Buddhists who, it must be assumed, aren’t familiar with Buddhism’s scriptures and who are only familiar with the modern idiom of teachers like Jack Kornfield and Pema Chodron. And when they see Fake Buddha Quotes they don’t have the basis of knowledge to recognize that the quote couldn’t possibly be canonical. But perhaps this one is too obviously fake for most Buddhists to be fooled by. Or maybe it’s just too new. We’ll just have to wait and see!
Where does this come from? I don’t know for sure. I’ve found “Your job is to learn how to respond, not react” in Louie Andersen’s “The F Word: How to Survive Your Family.” And in “Faces of Compassion,” by Taigen Dan Leighton I found “…learn how to respond appropriately and helpfully, without feeling overwhelmed or compelled to react impulsively.” But these, I suspect are just reiterations of the same basic them rather than prototypes of our Fake Buddha Quote.