Satan has several different reactions here, as he and Beelzebub converse and ponder their plight in Hell. They have fallen after the war in heaven and his first reaction is a sense of remorse, even guilt, for having failed his legion of followers, in particular Beelzebub:
...if he [Beelzebub] whom mutual league, United thoughts and counsels, equal hope And hazard in the glorious enterprise, Joined with me once, now mistery hath joined In equal ruin. (I.87-91)
Satan also demonstrates a sense of surprise at the power of God when he questions, "...so much the stronger proved / He with his thunder: and till then who knew / The force of those dire arms?" (I.92-94).
Finally, Satan takes a very Romantic position when he states that "All is not lost," which is curious since they both have just experienced the full wrath of God. Who would want to war in Heaven again after that? Well, Satan still seems to be up to the challenge and test that power of the Almighty again. Satan sees him as a Tyrant, "the tryanny of heaven" (124). But he is convinced, as he tries to convince Beelzebub that they should "wage by force or guile eternal war / Irreconcilable, to our grand foe" (121-122). Satan is willing to contest God forever.