The Sorrows of Young Werther - Johann Wolfgang von Goethe
“I could be living the best and happiest of lives if only I were not a fool.”
There are countless such wise and witty comments in this affecting tale of a young man suffering from the malady that is unrequited love. The word "young" in the title is the key, I think - our hero spends much of his time mooning around the heroine and bemoaning his unfortunate lot, much as most adolescent males do when they first fall in love. Crucially, Werther never loses the sympathy of the reader.
I gather that Werther is regarded as the first romantic novel focussing on the romantic travails of a self-absorbed protagonist. No Werther, no Adrian Mole. A sobering thought.