One love poem that is considered particularly sad is "In Memoriam A. H. H. OBIIT MDCCCXXXIII: 27" by Lord Alfred Tennyson, which ends in the famous lines "'Tis better to have loved and lost / Than never to have loved at all." Tennyson was a part of the Victorian period in poetic history, which is generally considered to contain a large amount of somber poems.
Victorian literature dominated the majority of the early- to mid-nineteenth century. In addition to Tennyson, many famous authors and novelists are associated with this style, including Charles Dickens, the Bronte Sisters and William Thackeray.
The Victorian era of literature nearly coincided with the Industrial Revolution. Many authors viewed this event as detrimental to all but the rich; as a result, themes of death, loss and misery are not uncommon in Victorian literature and Poetry. As can be seen in "In Memoriam A. H. H. OBIIT MDCCCXXXIII: 27," Tennyson views love and life as a tragic, but ultimately worthwhile, journey.
A similarly sad poem is "Isabel" by James Russell Lowell. Themes of death, longing and loss can be seen in this poem, which recounts the death of the author's love interest, Isabel. Stylistic differences can be observed between the two poems, both when considering meter and length of stanzas, but the content and style of delivery are strikingly similar.
Countless similar examples can be found in poems by other Victorian poets, including Emily Dickinson and Edgar Allen Poe.