Have you ever heard the story of the boy who cried wolf? He was a shepherd boy who cried out warning of the arrival of a wolf at least 3-4 times. His neighbors, each time came out to help him, and he laughed at them each time because there really was no wolf.
However, the 5th time the boy cried out, there really was a wolf. Because the boy had not told the truth the previous times, everyone assumed he was also not telling the truth this time, and his whole flock of sheep was devoured by the wolf.
The above story is a classic example of complacency. The neighbors of the boy had grown complacent with his cry due to the disappointment of his previous cries. They, in essence, learned not to believe him nor take him seriously. This complacency cost them all of their sheep.
This is how many have become in response to what God has said he would do because of the wait and the disappointments along the way. Many have become complacent in response to what God said he would do.