One key is not setting a final exit date, which would only allow the Taliban to wait out the US.
But it should also give Americans – also disheartened over this long war – a reason to hope for a life free of more Al Qaeda attacks.
The first and most sensible reason for optimism lies in Mr. Obama's decision to lay out a new exit strategy that does not also set down a final exit date.
His plan rests on a bold assumption that Afghans can start to better stand up to the Taliban – through a quadrupling of their Army, a campaign against corruption, and an uplifting of farmers – with the first handover of responsibility starting in 18 months.
But Obama also calculates that a steady hand-off of responsibility for security will not succeed if eternity-minded Islamic fighters know that US troops will withdraw before Afghan forces are ready. He has wisely tied a pullout to the Afghan forces meeting certain benchmarks for pulling themselves up by their bootstraps.
A second reason lies in the rapid surge of 30,000 more US troops by next summer – if complemented by an additional 5,000 troops from other NATO nations.