[37b middle] Gemarah: A and B together borrow one object from C. A makes the center of his Eruv 2,000 amos from the object (to be able to carry it 4,000 amos to its permissible limit at his intended end distant destination) and B makes the center of his Eruv 2,000 amos in the opposite direction. A and B are partners and each Eruv therefore combines with the other. Since there is no overlap of combined Eruv distance, it turns out that the object has ZERO distance of permissible carry-ability and neither A nor B can carry the object any amount of distance from its current location.
E’s Lesson: Many times when we try just to take only our own concerns into consideration, we end up losing much more than we even had to begin with. We must remember to give more than we receive, and work together to achieve.