As the comments indicate, this diary entry was private, and not meant to convey any message, except perhaps a reminder to its author. It is however characteristic of some central themes in Kierkegaard's philosophy (and life). Namely, coming face to face with your own existence, and its meaning or meaninglessness, through crisis and the contemplation of death.
One of the two main characters of Kierkegaard's first published work Either/Or (1843), Johannes the Seducer, also keeps a diary which might very well have contained something like the 1836 entry. In the work the "message" is the progression from hedonistic stage of life, leading through the crisis of meaninglessness and suicidal depressions to a more mature ethical stage. This said, one should be very careful with identifying Kierkegaard's views with any of his characters' and pseudonymous "authors", who often express incompatible and paradoxical views.
Here is from Watkin's commentary on Johannes the Seducer in Kierkegaard’s View of Death:
"After the party comes the hangover and the dawn of daily life, while the aesthete knows that his recollections are not really immortal but will perish with him. Kierkegaard’s young aesthete therefore lives in a state of suicidal depression punctuated by occasional frantic bursts of pleasure. Because he has become reflective enough to consider the question of the meaning of existence in the light of the fact of death his conclusion that it is meaningless has split him between wanting to live and die at the same time. It is encouraging however, that the young man has reached ‘the final aesthetic life view’ of conscious despair. Those who amble on unreflectively or blaming discontent on external factors are further away from truth than those who face up to their unhappiness and reflect about the meaning of existence."