After Duncan's death, Macbeth says "all is but toys". Explain what his words mean and whether they are sincere.

In Act II, scene 3, Macbeth, having just killed Duncan, observes:

"Had I but died an hour before this chance,

I had lived a blessèd time, for from this instant

There’s nothing serious in mortality.

All is but toys. Renown and grace is dead.

The wine of life is drawn, and the mere lees

Is left this vault to brag of."

Here, Macbeth expresses a fatalistic belief that in killing Duncan, he has robbed his own life of dignity, purpose, and meaning.  He is immediately remorseful, and his words are sincere.  He realizes that he has betrayed his king and country, and in doing so, doomed himself.  "All is but toys" expresses his belief that whatever he will do henceforward will be meaningless and transient. In killing Duncan he has discarded his own fame and respect. Whatever lays in his future will be a brief, trifling amusement. He believes that the best of life, living under Duncan's rule,  is behind him, and that he will never be able to rise to the nobility and morality of the great man he has murdered.