I attended a talk on Kierkegaard today. He was a Danish philosopher who lived from 1813 to 1855, not a long life today. When I look him up in Google, I see that he is often considered the first existential philosopher.
(From Wikipedia) "What is the theory of existentialism?
Existentialism is a philosophy that emphasizes individual existence, freedom and choice. It is the view that humans define their own meaning in life, and try to make rational decisions despite existing in an irrational universe."
What I heard today makes me think of the mental state or condition of depression, which I think is commonly treated today with ingested medicines. I looked up the question "Was Kierkegaard depressed?" Depression as a mood or mental disease has been labeled as one of the more easily treated conditions today. I was surprised to find that searching the question Was Kierkegaard depressed? brought many references from his own writing to the idea of depression, but I gather the man felt very sure his thoughts and goals and hopes came from God, and had to be taken quite seriously as given.
Our speaker explained that Kierkegaard was engaged to marry Regine Olsen but after a year of engagement, broke off the relation. I am no Kierkegaard scholar but I don't think that was wise. I gather he agonized and she agonized, but while she married someone else and lived a long and relatively happy life, he did not. From the little I know and have read, the man struggled deeply with his thoughts and feelings for years.