Consider the lilies...
So do not worry about tomorrow, for tomorrow will bring worries of its own. Today's trouble is enough for today. (Matt 6.24-34)
In her book With or Without God, which I reviewed a few weeks ago, Gretta Vosper alludes to this teaching, which she cites as one example of Jesus's teachings that we can no longer accept as valid. Her argument is that we cannot be "reckless about the future."
But what is Jesus really counselling here? Is he really saying that we should only think about the present, and not give any thought whatsoever to the future?
The verb that is used throughout today's gospel reading (Matt 6.24-34), merimnao -- translated here as "worry" -- means exactly that. It does not mean that we should not give any thought to the future, only that we shouldn't worry about it.
There is no upside to worrying: it never makes things better, but it often makes things worse.
The problem, though, is that being told not to worry rarely helps us stop worrying. We don't have a lot of direct control over our worrying. But the good news is that worrying is the result of other things that we do have control over.
Worrying and Desire
The Second Noble Truth of Buddhism is that suffering is caused by desire. In other words, reality is one way, but I want it to be another way. When this is true, suffering is the result.
I think Jesus's teaching about worrying is related to this. I want things to turn out one way, but it appears that things are going to turn out another way, so I worry. But what is this worrying? Is it not merely the suffering that results from my desire for things to be other than they are?
To end my worrying, I need to end my desire for things to be a particular way. This doesn't mean I sit passively and avoid working to attain the things that I need. It just means I don't form any emotional attachment to any particular end, or, where an attachment already exists, I let it go. The desire doesn't help, and worrying doesn't help. On the contrary, worrying often undermines our performance of doing what we have to do in order to attain the end we seek.
Anthony de Mello tells a great story, attributed to a Chinese sage named Tranxu (aka Chuang Tzu):
Or, in other words, keep your eyes off the prize, and focus on the task at hand.
When the archer shoots for no particular prize, he has all his skills; when he shoots to win a brass buckle, he is already nervous; when he shoots for a gold prize, he goes blind, sees two targets, and is out of his mind. (Awareness 58)1
 The wording in de Mello's book is very similar to that found in Thomas Merton's Way of Chuang Tzu, and I suspect that is where he got it from.