Doing an ordinary thing extraordinarily well? Says who?

From a sermon I listened to as a teenager, I remember this quote cited by the priest:

"Do every ordinary thing extraordinarily well."

The priest attributed it to Saint Teresa.

I've always wanted to verify the source of the quote, but I just couldn't find evidence that Saint Teresa actually said it.

My Internet search, though, resulted in quotes that are very similar, notably:

"Excellence is doing an ordinary thing extraordinarily well."

"Success is doing an ordinary thing extraordinarily well."

Putting today's blog and yesterday's together, one could say that two essential qualities for success are (1) making finer and finer distinctions about things, and (2) doing an ordinary thing extraordinarily well.