Why is halo so scary

I've been replaying all the halos and the games are just as I always remembered there so scary I don't know why but especially halo CE and halo 2 I just feel so scared like something is watching me or I'm lonely especially in halo CE missions like Halo or The silent cartographer it just seems so scary I can't play through the missions their just too scary does anyone feel the same way and when the flood comes the game either gets too boring or just really scary tell me your opinions please