Because it takes a long time for the predictable outcome to occur
Explanation:
This is a line from melo-drama called "Hamlet Dull Revenge" authored by Rene Girard.
The play examines the character called Hamlet who despite wanting to avenge his father, who was unjustly killed by Claudius, took his time to investigate the circumstances involved instead of engaging his mindless and wanton killings because of his desire for vengeance.
The author Girard, concludes that Hamlets tact is delaying vengeance is not a sign of weakness as vengeance is often a response to violence or injury to a loved person.
