It isn’t Christ’s project to teach believers about the material world, but about the world of the Spirit. Great errors in understanding Jesus stem from a failure to appreciate the nature of the classroom in which we find ourselves.
So, when Christ instructs us not to worry about tomorrow, we must not rush to put that advice to the world’s test. If we do, we will find it to be very questionable, and we will be tempted to qualify or interpret it, in order to render it compatible with common sense and everyday observation.
But Christ is not saying that worrying impedes worldly success; there is no such testimony from Him to be cross-examined.
The worry Christ wants vigilance towards is our intellectual preoccupation with the possibility that we are being deceived by our horror of meaninglessness. That horror is certainly real, but it lies deep, too deep by far for us to reach. Its assuagement must be left to the Spirit. But our deference to it is something over which we have at least some control, and that is is the object of Christ’s instruction for believers.