Vincent worked in the art trade with Goupil and Company for six and a half years in total, although we only have documentation of about four of those years. Initially, it seems that he enjoyed the work and thrived in the art business, garnering praise from his superiors. As in all endeavors, Vincent allowed his job to absorb him completely, only to abandon it suddenly in depression, frustration, and spiritual and emotional dejection, the first casualty of his unstable psychological condition (most likely bipolar disorder–also known as manic depression–or mild schizophrenia.) In 1872, Theo came to visit Vincent in The Hague, eliciting Vincent's first recorded letter upon his brother's departure, expressing his reluctance to see his Theo leave. In December, Theo began work at the Brussels branch of Goupil and Company. Soon afterward, in 1873, Vincent was transferred to London on a promotion, stopping in Paris to visit the art museums there, and Theo took his brother's position in The Hague offices of Goupil.
Vincent's first trip out of his homeland proved both difficult and exciting, and it afforded him the opportunity to be exposed to a wealth of English and international art. His interest in art history and literature (particularly Shakespeare) grew, and his informal education led to the formation of rudimentary opinions about the role and value of art. His reverence for the old Dutch masters (especially Rembrandt and Rubens) grew, while he simultaneously became attracted to the more contemporary landscape painting of the English artists John Constable, and William Turner, the important Realists Corot and Millet, and the work of Emile Wauters; he read Keats, Dickens, and Longfellow and relished the ecstatic romanticism of philosophical historian Jules Michelet. In general, he was not a great fan of English painting, but he was able to find much art, both old and new, in London, that he appreciated (much of which was, not coincidentally, the primary fare of Goupil's business) – particularly the work of the French Realist Barbizon School (which included Corot and Jules Breton) and the lesser- known Dutch equivalent, The Hague School. He explored the city on long walks that soon became a necessary routine in his life, eschewing the popular tourist sites for more authentic areas. He met his uncle by marriage, the painter Anton Mauve, whom he greatly respected and with whom he would study a few years later. Homesick but generally happy, Vincent had his somber moments even early in his life–he wrote to Theo in 1873, quoting Dickens, that smoking pipe tobacco was a "good remedy" for the suicidal thoughts he occasionally had (L five, Mar. 1873).
Vincent was a lodger with the Loyer family in Brixton, South London, and his earliest extant drawing is a sketch of his street. His choice of residence turned out to be unfortunate, however–in the spring of 1874, after a visit home to Brabant, during which he did a little sketching and a lot of reading, he declared his love to his landlady's daughter Eugenie Loyer, a pivotal episode that about which his family knew but about which Vincent himself hardly wrote, like most of his crises. Influenced by his favorite writer, Michelet, and his idea "that a woman is 'a quite different being' than a man" and that "there is much more to love than people generally suppose" (letter twenty, July 1874), he proposed to Eugenie, who was already secretly engaged. Vincent pursued the situation anyway, but was rejected, and this first taste of a long career of romantic failures, what he later defined as unbalanced "intellectual passion" (L 157, Nov. 1881) crushed him emotionally. His Uncle Cent had him transferred to Paris for three months as a distraction, but upon his return to London, and by his second, permanent transfer to Paris in May 1875, Vincent was completely miserable. His letters were melancholy and sometimes muddy or confused–he seemed passionate only when discussing painting and religion. He became more and more introverted and depressed, and the inclination towards religion that he had felt since a boy was steadily magnified, until he became profoundly spiritual, spending his nights studying the Bible, John Bunyan's A Pilgrim's Progress, and Thomas a Kempis's Imitation of Christ (L forty-two, Oct. 1875).
Vincent and his family both understood that his career was in jeopardy–his personal appearance became increasingly shabby, and his depressed, temperamental attitude and general apathy and carelessness with his work annoyed his employers and clients. Vincent left Paris without telling Goupil and Company to visit his family at their new home in Etten, The Netherlands, for Christmas 1875, and when he returned to Paris, he was fired effective April 1876. His distraught family was not excited about his move to England, where he taught briefly as assistant master to a reverend at a religious private school in Ramsgate. In July 1876 he took a position as an assistant preacher in Islesworth and delivered his first sermon, a moment that he considered a great triumph and turning point. The devout Vincent read, wrote, and walked compulsively in an attempt to understand his desperate psychological condition and his periods of spiritual ecstasy, and his unorthodox religious beliefs began to verge on Christian fanaticism, which worried his family, especially his pastor father. Vincent spent Christmas 1876 in Etten, and his parents managed to find him a job at a bookstore in Dordrecht, but he was as despondent there as he had been in England, and he spent his time translating the Bible, writing ecstatic, confusing symbolic sermons, and sketching.