According to Wikipedia, “An Achilles’ heel is a weakness in spite of overall strength, which can lead to downfall. While the mythological origin refers to a physical vulnerability, idiomatic references to other attributes or qualities that can lead to downfall are common.”
Discouragement is one weapon Satan uses to neutralize a leader. Not even Moses, the meekest man on earth was spared of this insidious tool of Satan. Many a time, the provocation of the people he led brought him to a sad end. At Sinai when Moses spent forty days up in the mountain, the children of Israel became impatient and backslide. They prevailed on Aaron to make a golden calf for them to worship. Right on the Mountain, God spoke to Moses that the people had corrupted themselves. Quickly, Moses began to intercede for the people, he pleaded with God to forgive them. When he descended the mountain and saw the golden calf with the people dancing around it, out of exasperation he broke the tablets of stone he had in his hands. Moses expressed his disgust to Aaron and the children of Israel. “When they came near the camp, Moses saw the calf and the dancing, and he burned with anger. He threw the stone tablets to the ground, smashing them at the foot of the mountain. He took the calf they had made and burned it. Then Moses ground it into powder, threw it into the water, and forced the people to drink it.” (Exodus 32:19-20 NLT).
Imagine the exasperation of leading a bunch of never appreciative murmurers. Twice they tried to stone Moses. First, was at Raphidim when there was no water and second, was at Kadesh when the ten spies brought back an evil report about the giants in the Promised Land (Exod. 17:4; Num.14:10). On each instance, Moses maintained his calm and interceded for them.
However, none of the above situations would have discouraged Moses more than the incidence at Kadesh when the children of Israel were faced with lack of water for the second time. True to their character, they murmured and complained before God. When Moses appealed to God on what to do, the Lord told him to gather the people and in their presence to speak to the rock that it would yield water for them to drink. But instead of speaking to the rock, Moses in anger struck the rock. This action cost him the Promised Land.
Moses on several occasions had through intercession prevailed against God, but not on this occasion. When he pleaded with God to allow him to enter the Promised Land, the response he got was an emphatic no. “Then I pleaded with the LORD at that time, saying: ‘O Lord GOD, You have begun to show Your servant Your greatness and Your mighty hand, for what god is there in heaven or on earth who can do anything like Your works and Your mighty deeds? I pray, let me cross over and see the good land beyond the Jordan, those pleasant mountains, and Lebanon.’ “But the LORD was angry with me on your account, and would not listen to me. So the LORD said to me: ‘Enough of that! Speak no more to Me of this matter. Go up to the top of Pisgah, and lift your eyes toward the west, the north, the south, and the east; behold it with your eyes, for you shall not cross over this Jordan.’”
(Deuteronomy 3:23-27 NKJV).