As long as you have just two horses living together you will find that they will miss each other’s company when separated. This is just normal horse behavior. How reactive they are will differ from horse to horse. And yes when reunited with other horses it is normal to settle down, though there are some horses that continue to look for their pasture mate. I am not sure I understand what you want to do with these horses and how their current behavior interferes with your goal. Also your description of working and resting is not clear to me; can you explain that further?
DrO