In the wonderful book, Ish Lirei'eihu, parashas Chayei Sarah, the following story is repeated as it was told by Rabbi Avraham Elyakim Shif z"l.

"When I spent the winter of 1941 in Siberia, a great Torah scholar, Rabbi Menachem Rotman z"l, died in the hospital. I went to perform the last act of loving-kindness for the deceased by burying him properly. A Mr. Zucker and I undertook it upon ourselves to dig a grave for him. However, we never fathomed how difficult it would be to dig in the middle of a desert wasteland which was totally frozen to a depth of 2 meters.

"We found an iron pole whose point was as sharp as a stake and we tried with all our might, which wasn't that much, to blunt the hard ground. To our dismay, sparks began to fly but the earth yielded only a fraction of a centimeter. After laboring for hours, our bodies drenched in sweat and suffering from the freezing wind, we had only succeeded in making a small hole in the ground. By nightfall, we had only dug 15 centimeters and we were totally exhausted having not eaten all day long.

"Realizing that we were not going to succeed, yet wanting so much to fulfill this great mitzvah, I turned to Hashem and began to cry and pray. 'Master of the Universe,' I began, 'we did everything we possibly could, and even more than that. What should we do now? We cannot leave the body alone in the desert yet we cannot possibly sleep here all night because of the deathly cold. We cannot return the body to the city since the wagon which brought it here has already left.'

"While I was crying and praying, an amazing thing occurred before our very eyes. Suddenly we saw two gentiles coming towards us with simple spades in their hands. Without realizing the ludicrousness of the question, since it was obviously impossible to dig this hard ground with the tools they had, I asked them if they would help us dig this grave. To our amazement, they immediately agreed and began digging. After only ten minutes, they accomplished what we couldn't do for hours with an iron spade! Flabbergasted, we asked them how much we owe them for their work and they surprised us again by asking only forty rubles, enough to buy only one quarter of a kilo of bread at that time. They took the money and disappeared in the darkness from whence they had come. We buried the Rabbi and thanked Hashem for sending us His help when we needed it most.

"As we trudged home, for fifteen kilometers, we began to digest what had occurred and to appreciate the miracle Hashem had performed for us. We realized that it was totally unnatural for two men to suddenly appear, so late at night, in such a barren place, with shovels in their hands; and to dig a grave so fast, under those conditions; and to ask such a small amount of payment.

"We realized then that that which we had been taught by our Rabbis was true. When one uses up all of his ability, but wants, with all of his heart, to fulfill Hashem's mitzvahs, he will be granted the opportunity to do so, even through supernatural and miraculous ways. If one is ready to give up and just say, 'I can't do it,' then he will lose the opportunity. But if he insists that he wants to succeed but simply does not have the tools with which to finish the job, then Hashem will supply those tools which he lacks and he will even be able to accomplish the impossible."

Then he will be truly happy, in this world and in the World-to-Come.