As a result, people are always confiding in him. Nick first thought that he was worthy of much scorn. Nick realizes that it was, in fact, other people who are worthy of scorn. It is these bad people who made Nick stop wanting to reserve judgment.
Abortive sorrows are half-sorrows, unfeeling sorrows, fake sorrows.
Short-winded elations of men, are partial, incomplete, elations. An elation is a great joy. Nick Carraway sees himself as a man who reserves judgment. As a result, people are always confiding in him. Nick first thought that he was worthy of much scorn.