Re-sawing the sawdust is the practice of asking the "What if" questions of our lives. It is reliving the situations we wish we had handled differently and avoiding the regrets that we live with. If only we had not done.... If only we had handled a situation differently. If only we had not suffered the situation we walked through. If only.
Here is something to remember. None of us get to the end without regrets, failures and situations that are painful. But the sawdust is already in a pile on the floor and there is nothing we can do about it. We are fallible, sinful, sometimes foolish and often wrong. The only thing to do with the sawdust is to give it to God, ask forgiveness if necessary and live in His grace and mercy - which according to Jeremiah is new every morning. You cannot re-saw sawdust.
Asking the "what if" questions is a waste of time since we cannot do anything about them except learn from them. And that wasted time is time we cannot invest in making wise and productive choices regarding our future. The past is past and there is no redo. The future is a wide open vista with unlimited possibilities. It is where our focus should be.
When Jeremiah wrote the words "Your mercies or compassions are new every morning, Great is your faithfulness," he was standing in the rubble of the destroyed city of Jerusalem. Rather than focus on the disaster that surrounded him, his focus was on the mercies of God and God's faithfulness today and tomorrow. At that moment he was not looking back but looking forward based on the character and love of God. Jeremiah was declaring that all was not lost. His mercies are new each day and His faithfulness is great. Repentance for the past sins was part of his equation but living in the past was not (Lamentations 3:22-24).
Those who have the hardest time letting go of the past are those who tend toward perfection. Failure, mistakes or not getting it right are deeply painful to them (I count myself in this company) and just letting go and admitting they screwed up is tough. Those who live in their head find themselves reliving the events over and over and over.
For those who know Christ, we can leave our past at the cross. If it is a matter of sin He tells us that He fully forgives. If it is a matter of mistakes made He tells us we are human - it happens. If it is a matter of illness or those things we have no control over, He tells us that His faithfulness is great. If it is infused with pain, regret, sadness and depression He says His mercies are new every morning.
If all those things are true, we need to discipline ourselves to look forward and not backward. Every time you start looking back, remind yourself - Jesus has it - you left it at the cross. There is no better place to leave everything.