"As long as I could stay in the light, figuratively speaking, by keeping my focus on what I could control, worry and fear were kept at bay.

That's why I pinned my concentration to the tasks in front of me, not letting myself agonize about the grade of the hill I was pushing our unwieldy ride up, but studying every crack and crevice in the concrete, studying the sounds of the stroller wheels, noticing I could move to that syncopated beat.

Sometimes the effort made me happy, it let me dance when some might have said I had nothing to be happy about." 

Chris Gardner, The Pursuit of Happyness