Why This 'Woe Is Me! For I Am Undone'?

Isa 6:1 In the year that king Uzziah died I saw also the Lord sitting upon a throne, high and lifted up, and his train filled the temple.
Isa 6:2 Above it stood the seraphims: each one had six wings with twain he covered his face, and with twain he covered his feet, and with twain he did fly.
Isa 6:3 And one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory.
Isa 6:4 And the posts of the door moved at the voice of him that cried, and the house was filled with smoke.
Isa 6:5 Then said I, Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, the LORD of hosts.
Isa 6:6 Then flew one of the seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar:
Isa 6:7 And he laid it upon my mouth, and said, Lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin purged.