The word "those" is confusing. Here's what he means to convey, I think:

"Seek out habits that help you overcome fear or inertia. Destroy habits that do the opposite."

Habits that do the opposite are habits that cause us to become prey to fear or inertia. In short, habits that keep us stuck, unwilling to take chances, cowering in life's back corners.

That's my read, anyhow.

Offtopic but I wonder what he means by this:

"Seek out habits that help you overcome fear or inertia. Destroy those that do the opposite."

Agree with above. Dunno if he's Paleo, but I know he was doing CF a few months ago. Why don't you ask him on his site? He'd prolly reply.