I wasn't thinking about that verse but it's fantastic.

One of the benefits of attending a strongly biblical church (thirty years for me) is that you can't help but being brainwashed (but in a good way) over time. The Bible calls it the renewing of one's mind (Romans 12). After a while there's an inherent sense of biblical vs. non-biblical behavior. One doesn't need to search for a verse to understand how to react to things as it becomes one's nature.

And of course being open to be led by the Holy Spirit is key. But one has to know the Bible to understand if something is truly of the Lord. The Holy Spirit is the author of the Bible and He doesn't contradict Himself. So if one is questioning if something is of the Lord, but it contradicts scripture, it's an easy call.