From Midrash Bereishit Rabba 78:7:

Rabbi Levi provided a parable:

It happened that the lion, king of the wild beasts, was angry with his subjects. So all the animals called a conference, the theme of which was: “Who will go to appease the king for us?”

The fox volunteered. “I have 300 very clever parables,” he said. “One of them will surely appease the king.”

The animals enthusiastically approved, and they accompanied the fox on his way to the king.

Along the way, the fox abruptly stopped. “What is wrong?” the animals asked him.

The fox replied, “I’ve forgotten one hundred of my parables.”

“Only one hundred!” they replied. “You have two hundred more. Surely the king will be appeased with two hundred clever parables.”

So they went on. But as they neared the palace of the lion, the fox stopped again. “What is wrong?” the animals asked.

The fox replied, “I’ve forgotten another hundred!”

“Only two hundred!” they replied. “You have one hundred more. Surely the king will be appeased with one hundred clever parables.”

So they went on and entered the palace. As they stood in the ante-chamber, about to be called into the king, the fox shook his head. “What is wrong?” the animals asked.

The fox replied, “I’ve forgotten all of them!”

“All of them?” the animals replied. “Now what will we do?”

“Now,” the fox said, “each one must enter and plead for himself.”

When the Baal Shem Tov would repeat this parable, he would explain that the fox never intended to tell his 300 parables. This was only a ploy so that he could bring them all to the king, and then each one would have to speak for himself.

And, the Baal Shem Tov concluded, the fox did well.

So it is with the tzadikim who pray on your behalf, the cantors who inspire you in the High Holiday prayers, and with any true mentor who may guide you in life. They will only take you to the door of the throne room. The rest is up to you. You must create your own relationship with your Maker.

The Baal Shem Tov would then continue with another parable:

Two kings fought a war with one another. One king was extremely powerful and commanded valiant knights of armor, skilled in the art of many deadly weapons.

The other king also sought to enlist such valiant heroes for his army. He searched throughout his kingdom, but to no avail. No one had such skills or knew how to attain them, and the smiths of the nation didn’t even know how to forge such craft.

Finally, that king told his people, “We have no weapons but those you hold in your hands, and no heroes to rely upon but ourselves.”

And with those words, all his people became heroes.

So too, as well, with a tzadik. The tzadik can show you the way. He can even hold your hand and lead you to the battleground. But it is up to you to be a hero and fight to win.

Keter Shem Tov, siman 35. 133.