Inertia (관성) is something that always gets in the way when you want to change. Something you want to start doing, you're not just used to it. Something you want to stop doing, you somehow keep doing it 'cause it's like a habit. It frustrates you, and somehow even makes you wonder if you lack the proper will power to change. It can be scary like that.
I'm going through a couple of changes now, and this is almost knocking me over left and right. Well, I have the necessary persistence at least, so that'll help me keep diligently going (정진).