7. It is a sin to do less than your best. It is wrong to do [merely] well.
“Whatever your hand finds to do, do it with your might” (Ecclesiastes 9:10 ). But be careful. Sometimes the “best” is a B+ sermon and spending time with your child. In other words, “best” always involves more decisions than the one you are making at the moment. That one means many other things are being left undone. So “best” is always the whole thing, not just the detail of the moment.
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I like how John Piper says we must do our best, with all of life and not just one part to the sacrifice of all the rest. So I’d start with doing your best in your relationship and communion with Christ, and then let him set the priorities and responsibilities for your life and do your best taking all of them into account and the relationships between different priorities and responsibilities. This is an encouragement and a challenge to my soul.