What does Romeo mean when he says, after killing Tybalt, I am fortunes fool?

In
, 's fatalistic nature is established early in the first act when he
expresses his misgivings about going to the Capulet fete:

I fear too early. For my mind misgives

Some consequence, yet hanging
in the stars,

Shall bitterly begin his fearful date

With
this night's revels, and expire the term

Of a despised life closed in my
breast...(1.4.113-117)

So, analyzing Romeo's remarks in
the context of his character and not just the statement of the moment, which will provide more
insight, the reader discerns that Romeo is haunted by his previous forebodings and now
understands that the "fearful date" of the stars has come; consequently, he realizes
that he is a "fool" since he has earlier sensed the ominous presence of Fate, and,
acting rashly and with effeminency--as he accuses himself--he has allowed himself to meet its
"date."