THE CHAPTER BEFORE US (JER. 20) provides insight both into Jeremiah's external circumstances at this stage of his ministry, and into his inner turmoil.
(1) Jeremiah's external circumstances: the priest Pashhur son of Immer is the "chief officer" in the temple, presumably the chief security officer, serving under the current high priest. The prophetic actions and words Jeremiah has delivered in the previous chapter, announcing the destruction of Jerusalem and its temple, have been interpreted as something near treasonous, if not blasphemous, the more so because Pashhur has been among those who have "prophesied lies" (Jer. 20:6) to the effect that God would never let this city fall to the pagans (cf. Jer. 14:14-15). So he has Jeremiah arrested and beaten, presumably with the legal limit of forty stripes (Deut. 25:3---that number was reduced by one in Paul's day to ensure that the limit was not accidentally exceeded, 2 Cor. 11:24). Jeremiah spends a night in the stocks, devices guaranteed to cause the terrible pain of cramped muscles. By the next morning Pashhur has second thoughts and lets Jeremiah go. If he thinks this leniency will reduce the prophet to cowering jelly, he is mistaken: Jeremiah uses the occasion to assign Pashhur a new name meaning "terror on every side" (Jer. 20:3-4)---another picturesque anticipation of the judgment sure to fall, when all of Pashhur's false prophecies will be exposed for what they are.
(2) Jeremiah's inner turmoil: if the prophet is outwardly courageous, the following verses (Jer. 20:7-18) disclose something of his personal anguish. By this point Jeremiah has been predicting judgment for decades, and it has not yet fallen. It has become progressively easier to dismiss him and mock him. The Lord's forbearance becomes an excuse for cynicism (as in 2 Pet. 3:8-9). Jeremiah temporarily resolves on silence, but so strong is the prophetic word burning within him that he cannot hold it in (Jer. 20:9). So he speaks, and his erstwhile "friends" listen with sneering condescension, hoping he will say something that will enable them to report him to the authorities and get this silly man into trouble (Jer. 20:10). Jeremiah oscillates between a focused and brilliant faith utterly confident that the Lord will finally vindicate him (Jer. 20:11-13), and a debilitating despair that frankly wishes he had never been born and wallows in understandable self-pity (Jer. 20:14-18).
Perhaps there are some servants of the Lord who have never experienced such highs and lows. But they are rare. Certainly those who serve in hard places almost invariably mirror Jeremiah's experiences in some degree. Pray for Christian leaders, especially those whose patch is profoundly discouraging.