I am strengthened by the delightful optimism of this man.
Os quotes George Whitefield saying, 'I'm never better than when I'm on the full stretch for God.' Here's the full context of that statement, which comes from Whitefield's Journals (Jay Green, 2000), p. 81.
Expounded, in the evening, to above a thousand hearers of all denominations; supped with General Columbine; and went home betimes, full of unspeakable comfort. I am never better than when I'm on the full stretch for God. God grant that I may not, like Jehu, drive furiously at first, and afterwards fall back; but 'forgetting those things which are behind . . .' (Phil 3).Mark Dever interviewed Os here.