@MickMac, in a way this is the Camino, for many of us. I am a 6-timer too and have regrets of the same kind. The realization usually sets in long after returning to "normal life", in my case often when I finally get to edit my trip video or when I review pictures. For sure there are those people that I parted with very intentionally for a reason: No regrets whatsoever.
It's usually the quiet, nice, and interesting comrades that I somehow suddenly lost on the way, those I would have liked to know better. Often people with whom I shared only a fleeting exchange, even just an emphatic glimpse of an eye. But then we all have our agendas, concerns, and priorities. On the Camino, we become much more sensitive than in our everyday life.
Let it go, remember and smile when you do or when you look at your pictures.
Camino #7 will give us a chance to do it better!