Elijah battled depression. Jeremiah was thrown in jail. The disciples were martyred. Even the great apostle John, wrote his Revelation from a prison compound on the isle of Patmos. And let's not forget, that our Lord was despised and rejected of men and was mercilessly crucified.
Disappointment comes into our life.
Things don't always go the way we expect them to. People we love die. We don't always get the credit we deserve. Sometimes we are victims of injustice. Sometimes life is a struggle.