This comes from John Piper’s book A Hunger for God. All of us have people we admire in ministry, and all of us will experience success at some point in our ministry. This is a great warning for either:

It is dangerous to hold up a person or ministry or church as a model…As soon as we do, the clay feet will become plain. Disillusionment often follow naive admiration. There is none without sin, and all our triumphs are mixed with imperfections. We do well to temper our esteem with the acknowledgement that there are hidden faults in any saint, and today’s victory is no assurance of tomorrow’s holiness. Nor can we even read the heart of today’s triumph. Neither the heart of others nor our own (1 Cor 4:4)…

God alone never changes, but the outpourings of his blessings ebb and flow in some ways far too mysterious for our minds to judge. The moment we think righteousness holds sway, some sinful plague is spreading in the midst. And just when we think the darkness is so thick that all is lost, someone grabs a rope that rings a bell and brings an army with torches. We will only maintain our stability and unshakeable confidence if we keep our focus on the unchanging God and take every rising and receding tide as a work of infinite wisdom for the accomplishment of His holy purposes.