Many people will realize that they have neglected Jesus' repeated warnings to be ready for His Coming.

.......................Matthew 25:13
"Watch ye therefore, for ye know neither the day nor hour wherein the Son of Man cometh."

...............This warning was given at the end of the parable of the Five Wise and the Five Foolish Virgins, where Jesus showed that a good amount [half] of professing Christians who will be waiting for the Bridegroom will not be ready when He comes.