I think that it is clear that fear and insecurity is a major theme in this book. Just look at what Crusoe does right away when he finds himself on the island.
After his first night up in the tree, he starts to build himself fortifications. He spends so much time on this -- without many tools he pounds stakes into the ground in a half circle that is 8 yards deep and 16 across. That's a huge amount of stakes!
Later on, he plants all those trees in front of his home to make it impossible for people to approach. He makes himself his "country home" just in case and then he starts using that cave as well.
On the other hand, you can argue that he's pretty bold with regard to people. After all, he gets himself all ready to go and try to kill 20 cannibals before he talks himself out of it. And he really does kill a group of them with Friday's help.
So fear is not the only thing going on, but it certainly is important.