Whenever I think about our intractable military commitments, I consider the fallacy of sunk costs. People believe we owe something to the past by continuing the fight in the name of honor or dignity. The reality is that the costs of war will never be repaid. We should only make decisions based on future payoffs. The toothpaste rule applies - what’s done is done and those entries are in the ledger, for better or worse. 

Some people will say we should have stayed in Afghanistan to honor the sacrifice of those who died or were injured so it wouldn’t have all been in vain. Ask the dead or the living if our continued catastrophe for their sacrifice is any consolation. Economically the right thing to do is cut your losses. Morally, sparing other people the same fate as those who sacrificed needlessly feels like a greater way to honor those who suffered.