FAKE IT TIL YOU MAKE IT
There's adages that all promote the same kind of idea:
The idea is that we often never start as something (ie - strong/fit, well-spoken, faithful, etc.), but through a series of making decisions to be something we eventually become that (ie - strong/fit, well-spoken, faithful, etc.).
Paul is making a similar point about being filled with the Spirit in Ephesians 5:15.
EPHESIANS 5:15
Paul is connecting marvelous ideas (God building a spiritual house of Jews and Gentiles) and mundane ideas (God's instructions for this house and the household that makeup this house).
And a bit at the connecting point he says:
"15 Be very careful, then, how you live—not as unwise but as wise..."
In a way, Paul is echoing the idea of "be it before you become it," because this is what Paul knows:
...outside of Christ.
As a result, becoming wise requires learning to be wise by making one wise decision at a time (ie - "live as though you were wise.)
THE SPIRIT IS WISDOM
At my roots, I'm what folks would call a charismatic Christian.
I tend to always anticipate that the Spirit can show up in powerful, unique, and unexepcted ways.
At the same time, I've learned that while the Holy Spirit can be marveled at - He isn't a bag of magic tricks. Instead, the Holy Spirit is more often than not, filling us to mundane things (not marvelous things) with excellence.
That's the main idea here.
When the Holy Spirit fills us, we begin to make small, sequential decisions to be wise in all kinds of areas:
All of these things (and more!) require acting "as wise" not "as unwise."
A great Pentecostal prayer would be, "Holy Spirit, fill me to be wise."