Bach got fired a lot; or rather, "encouraged to explore outside career choices". In August 1703, at the tender age of 18, when most of us, still living at home, cranked the Rage or Avenged to purposefully chagrin our parents, Mr. JS Bach received gainful employment, through family ties, as the church organist at Arnstadt.
Teenage rebellion, and finding oneself, was no different then as it is now; and Bach, as an unruly teenager both aware of his genius and willing to flaunt it, found himself with an organ tuned to play any chord he wished, which is kind of like giving a metric tonne of blow to a cokehead.
At first, he played the chorale sections dutifully; always playing the pure chords, never embellishing, ensuring the staid, Lutheran congregation could follow, and sing, without complication. But a man of Bach's talents is not easily subdued, and soon, he added embellishments to the chorales. Nothing much, maybe a 32nd note run between chords, a few extra trills, or a throwaway seventh chord in between; but his quick mind was racing, and with every addition gone uncommented upon, he gained confidence and added a little more each time.
You can almost picture his anticipation, waiting for the long-winded Lutheran pastor to finish his sermon, so he could unveil the chord progression he had worked on the previous night into the wee hours, tossing florins at the young air pumper to keep on pressing. And sure enough, the pastor has chosen yet another bland recitave, Nun freut euch, lieben Christen Gmein (Dear Christians, one and all rejoice). Luckily, Bach figured this would be the case, and is prepared; the congregation picks up their hymn books, poorly printed in the style of the time, and awaits the first chord to begin singing.
Except, he has different plans. He lets loose a torrent of sixteenth notes, in the soprano, and eighth notes in the bass, played at an almost prestissimo pace. And after three and a half bars of indulgence, he begins the cantus firmus in the tenor, signalling that the congregation should start; and they do, hesitantly, for the deluge of sixteenth notes continues, over the cantus firmus, almost as an afterthought, supporting the chord but seeming wild, unleashed, as though the slightest wrong fingering could send the whole piece to oblivion.
The congregation sings along because that is what good Christians should do, but Bach has clearly lost himself in the music; in between lines, he switches chords two, three, even four times; and even when it seems he has completely lost his marbles, he resolves his chords to the good cantus firmus the whole congregation knows. And when the brief, minute-and-a-half recitative ends, Bach cools his wrists; the pastor gives him a sour look, and continues with his sermon about adultery, or wickedness, or God knows what other sin the German needs to be enlightened about. Pride, certainly, in Bach's case. But he just sits there, grin on his face, knowing that he's slowly shattering the preconceptions about Western music, one bar at a time; and the two or three music lovers in the audience resolve to return next Sunday for mass.
Bach receives a proper tongue lashing after the mass, and apologizes for his wickedness; knowing, as usual, that he has something else in store for next week.