I suppose the two "things" can't mean the same thing as they introduce squarely opposite ideas. It might be saying that, to keep things the way they are (i.e. not to let them get any worse), people (either a certain group being referred to or mankind as a whole) should change the way they operate. In other words, things don't stay the same but constantly deteriorate unless you make an effort (work) to keep the existing state (i.e. a life form must find food to survive, a building must be regularly repaired not to crumble down, tribesmen must defend themselves not to be enslaved by another tribe, etc). The quotation seems to say the situation is worsening because "people" are not doing enough, and that they have to change their current ways to keep things under control. So in this interpretation, the first "things" means how things are (the current condition of life), and the second what people are doing now to control their destiny. It's just the impression I got from reading it for the first time, so I could very well be wrong.

What dId you understand? This quote is from a book called Il Gattopardo. In italiano «Se vogliamo che tutto rimanga come è, bisogna che tutro cambi”