“The point of this good-day-bad-day comparison is this: Regardless of our performance, we are always dependent on God’s grace, His undeserved favor to those who deserve His wrath. Some days we may be more acutely conscious of our sinfulness and hence more aware of our need of His grace, but there is never a day when we can stand before Him on our own two feet of performance, when we are worthy enough to deserve His blessing.”