Claudius indicates to Hamlet the impermanence of life. He talks about how everybody’s father must die: it is the way of God and nature. Claudius tells Hamlet that while it is honorable to mourn for one's father, it is against God and nature to mourn too long or obsess about it.
Tis sweet and commendable in your nature, Hamlet,
To give these mourning duties to your father.
But you must know your father lost a father,
90That father lost, lost his, and the survivor bound
In filial obligation for some term
To do obsequious sorrow. But to persever
In obstinate condolement is a course
Of impious stubbornness. 'Tis unmanly grief.
95It shows a will most incorrect to heaven,
A heart unfortified, a mind impatient,
An understanding simple and unschooled. act 1 sc 2