I got really sick of myself recently, noticing how I started telling people over a year ago that "my kids don't really get along anymore." Finally it occurred to me that I don't even know if that's true. So I started paying attention to how often they *do* get along (which is actually still almost always) and sort of informally timing how long the fighting episodes last (which it turns out are usually about 1-2 minutes each, unless I intervene by shouting and threatening, which makes them each last about 20 minutes, plus I end up feeling like a total psycho.)
So, there you have it! Often things are just a matter of perception.