So sorry this happened. You handled it really well.
It is just a job yes, and if we thought about the wives too much most of us wouldn't be able to do it at all. Just remember you haven't done anything wrong, it's HIS marriage and HIS choice to cheat.
I once had a long-term relationship with a married man in my personal life, and when she eventually busted him all hell broke loose. I sat and watched their lives fall apart, and my own too. I felt absolutely terrible, the guilt was unbelievable. But even in that situation, when there was actual feelings involved, it was still ~his problem~. He had broken her heart, and mine, in such a tragic and awful way.
It's just work. You haven't done anything wrong.