When Spike fell down, he didn't expect to survive. But once he discovered that he did, however, he began to explore. Needless to say, he wasn't exactly expecting the first living thing he ran into to immediately try to kill him, along with the majority of the population underground shortly afterwards.
However, despite this, Spike knows there's hope, as he meets several peaceful monsters along the way as well that wish to be his friend. He is now determined to make it through peacefully without hurting anyone, despite the world seeming to be against him. At least, that's one way the tale goes...