What does this mean?

15 In this meaningless life of mine I have seen both of these:
a righteous man perishing in his righteousness,
and a wicked man living long in his wickedness.
16 Do not be overrighteous,
neither be overwise-
why destroy yourself?
17 Do not be overwicked,
and do not be a fool-
why die before your time?
18 It is good to grasp the one
and not let go of the other.
The man who fears God will avoid all extremes .

Ecc 7:15-18