But what about the rest of the waking hours in the week? What does it look like (outsider view) to be a follower of Rabbi Jesus, man of the Galilee and carpenter? And what does it feel like (insider view) to walk a Christian walk from day to day in good times and in bad? Seen from the outside there may be times when such a person seems modest about themselves, but perhaps is forthcoming when asked about God (three in one). Polite, tidy, and behaving nicely quickly come to mind in free association of "Christian," but those are incidental to what is going on in the person's heart, whether by habit or with mindful purposefulness.
Of course a person grows physically and spiritually in the course of life experiences, whether they are first-hand or observed in others through by-standing, word of mouth, writings or other recordings, fiction or non-fiction, prose or verse, sung or spoken. Perhaps this spiritual maturation follows similar direction no matter the discipline or details of the religion: as a result of firm foundations, the person is able to accept wider and wider divergence from doxa, less black-and-white situations and yet be guided through on a steadfast course. Tolerance for ambiguity and ambivalence expands and the ability to live with doubt or unknowable things grows, too.
And so, when asked what it means to be a Christian the rest of the week, outside of worship services and organized or spontaneous acts of charity and love for fellow creatures, perhaps it comes down to this: such a person makes sustained and repeating effort to open her or his heart to hear the Will of God, to be aware of the voice of one's ego or that of the Tempter, and turn the other way and respond to God's call at each instance. Being governed by God's will and the commands to Love God, as well as to Love Your Neighbor as You Do Yourself, certain decisions and reactions from such a person may puzzle someone governed by consumer efficiency or the dictates of maximizing fun or pleasure.
So don't miss a chance for fellowship and glorifying God on Sunday morning, but that is not the place where one's Christian road lies. That walk is outside the walls of the worship room.