In the wonderful epic the Ramayana, Ram's wife, Sita, is kidnapped by a huge demon who lives in the island fortress of Sri Lanka. Hanuman discovers where Sita is hidden, but Ram's army cannot reach Sri Lanka because they have no way to cross the ocean. So they start building a bridge across the ocean. This bridge is still visible under the ocean in NASA photographs from outer space. Ram's army consisted of various Gods who incarnated as bears and monkeys. They all had enormous strength, and were capable of carrying many enormous boulders and hills.
While this construction was going on, small squirrels were seen carrying pebbles, roots, and twigs to assist in the construction. Some of the monkeys and bears started to laugh at this sight. Others wanted the squirrels to desist from the work, fearing that they would get trampled underfoot or smashed by the huge boulders the bears and monkeys were carrying.
Rama, on the other hand, took the matter very seriously. "No one is too small to assist Me in my work" he said. He let the squirrels continue their loving service.

Mother Teresa said "We cannot do great things, we can just do small things with great love". Like the squirrels, maybe we cannot do great things, but we can still serve God's purpose in our own small way.