Christian existence is a strangely relaxed kind of strenuousness, precisely because the Christian gospel is what it is. Before ever any demand is made, the gift is offered: the announcement of good news precedes the challenge.
The indicative precedes the imperative as surely as the rope is made fast round a firm piece of rock for the climber’s security before he has to apply himself to the struggle. Moreover (if the parable may be extended one clause further), the climber must attach himself to the rope before starting his effort. So the gospel not only begins with the indicative statement of what God has done, before it goes on to the imperative: even the imperative is first a command to attach oneself, before it becomes a command to struggle.
The striving does come: strenuousness is indispensable for the Christian climber—but only in dependence on all that has first been given by God and then appropriated through the means of grace.
--C. F. D. Moule, “’The New Life’ in Colossians 3:1-17,” Review and Expositor 70:4 (1973), page 479 [ht]: