I will say at the outset that, in answering this question, I’m defining “holy” not as we colloquially do now as basically “without sin” but in its earlier sense of “set apart.” That is, the question I’m asking is, To what extent does God want us to separate ourselves from the world? And by that I don’t mean does God want us to be worldly in the sense of adopting the world’s values instead of His — of course He does not — but does God want us literally to separate ourselves by living as hermits or monks or something like that, and spending all our time praying: praising God, confessing our sins to Him, and so forth.
David, a man after God’s own heart, certainly didn’t live like that and, perhaps more to the point, neither did Jesus. What’s more, we can’t follow Jesus’ Great Commission to us and spread the Gospel to the ends of the earth if we’re holed up in a cabin out in the woods somewhere, and we haven’t been told to stop being fruitful and multiplying either.
John the Baptist was a stout fellow and he lived an ascetic life in the wilderness, but to my knowledge he didn’t urge others to live like him, and the early Christians did not disengage: Paul kept repairing tents, and he and the other epistle-writers didn’t tell their congregants to quit their jobs.
And yet. It is also clear from the Bible, from the way someone like David and certainly Jesus lived, that God is always to be on our minds. And I think it’s also clear that most of us do need to work on being more “mindful” of God, to use the jargon du jour: thanking Him, adoring Him, confessing to Him, asking for His help a lot more throughout the day than we now do. Per Einstein, we should live like everything is a miracle rather than like nothing is.
And, by the way, I think this complements and fits in well with the extent to which God has chosen to reveal Himself to us. On earth now He’s not dramatically and undeniably in front of us — as He will be in Heaven — so that ignoring Him or doing anything other than worship Him is simply unthinkable. Rather, His presence is more subtle and the miracles often easily missed and, perhaps for long stretches in our lives and even in our history, He seems hidden. So we are to exercise our free will and rely on non-supernatural powers as we go about our quotidian activities. But we can do that and still keep Him more in mind than most of us habitually do.
We have to work on that.