"If God keeps tabs on our sins, O God, who can stand?"
This statement appears in many of king David's psalms in different forms. "God, You can't possibly expect us to succeed in this game of life? You cannot employ Your harsh rules of rewards and punishments since it would mean the end of humankind! God, if You didn't invoke Your concept of teshuvah and the capacity to redeem our sins, surely we would not survive! God, do You really want us dead? Surely, You would rather us alive and praising You?
All these weak arguments produce images of a guilty defendant standing before the judge conjuring up last ditch reasonings which have no logic and value for the executioner. Does God need our existence? Are we that impotent, unable to live a semi-successful life? If God made it too hard for us, why did He bother? Does He need our praisings?
The word tishmor תשמור translated as 'keep' is unclear. Not because we are unsure of the proper translation as we have ample contexts to observe, but because in our context other words would have better conveyed the point. תספור, תמנה, תפקוד, count, list, recall...
Tishmor connotes guarding, protecting; why would the author of the psalm phrase it in this way--if our sins guard you God, who would stand?
The question perhaps relates to how to view and judge people. If you look at someone and immediately see their deficiencies, their errors and their capacity for evil, you will very quickly have no friends. Nobody wants to be around a critical, preachy, though honest, individual. People are aware of their own misgivings and each one of us struggles with self-improvement. But to hear it constantly from our spouse, our parent or our child is enough to make us go very far away from them.
Seeing and focusing on the deficiencies of people is a way to guard yourself and raise your status above others. Keeping tabs on people might lead you to a more comfortable and confident self-perception. (I wonder if this is not the fascination in the media for reporting all the dirt that's fit to print. Why must I constantly have a tally of the murders, rapes, thievery and corruption in my headlines?)
What I am saying then is that seeing good in others is not a reflection of your righteousness but rather a psychological therapy for personal development and maturity. When you choose to focus on others' capacity for good you raise your own standards and seek to live a more meaningful existence.
To return to our poem. Our psalmist has sinned. He is in the throes of punishment and pain, the depths of darkness due solely to his wrongdoing. From those depths he calls out to God, pleading, demanding to be heard, to be attended to, to call out to God. What does he say?
"God, do not guard my sins, do not let my capacity for evil envelop Your perception of me. I may be down but I can rise. I can repent, I can hope..."
"God, teach us how to look not on the negative side of others, but on the potential they have inside to come back to Your grace. If You were to be cynical or realistic about the human endeavor--who could stand before You?"
Instead, our supplication before God in our moment of need is to reassert His position of optimistically leaning towards the capacity for good in humans and in so doing, teaching us to ultimately emulate His ways and shape our human condition based on this guiding principle.