One of my perfect “See and Avoid“ examples comes to mind. While flying a Cessna 180 at the correct VFR altitude of 8500’, I saw a Cessna 172 also flying at the same altitude, which was the wrong altitude for his direction of flight. The 172 maintained the same position in my windscreen as we got closer. When it started getting too close for comfort, I made a slight turn toward his tail and rolled out. That was enough to make his plane move from left to right in my windscreen. I passed safely behind him, experiencing a slight bump as I passed through his prop wash. We passed close enough that I could see the pilot staring straight out the front of his plane. He never knew I was there. Had I not been watching and made the course correction, we would have occupied the same piece of airspace. So, yes, “keep your head on a swivel” and “See and Avoid”.Derek Johnson, my glider instructor, used to say, "Head on a swivel!" to remind students to maintain awareness of the airspace.