I'm going to give a different opinion. I'm talking from the point of view of a masochist.

I don't think crying in a session equates to being broken, but it's probably a signpost on the path. I've been brought to tears from pain in several sessions. To me it's beautiful to get to a place where tears are rolling down my face, but I'm still be able to look into a Domme's eyes, thank her and ask for more. Tears can be a normal part of processing a scene. The word broken suggests something is wrong, we've passed out of the realm of logical response. At the beginning of a torturous session I can take the pain in stride. Evidence of pain is minimal and I may encourage or patiently wait for a Domme to increase the intensity. Then we get to the point where my distress is obvious. I'm making sounds, I'm writhing and pulling at bonds, I may start to beg. A lot of this is unconscious. I don't decide to pull at my bonds, I struggle to stop myself from doing it. Then we hit tears, crying is truly crossing a barrier into new territory, but it's not the same as broken. It's just another subconscious form of resistance, appealing to a Domme's empathy. Broken is still quite a bit further down the road. It comes when the acceptance of true futility sets in to the subconscious. Crying stops, begging stops, writhing stops and your subconscious just gives up and accepts that there is nothing to do but absorb the pain. To be clear, this is not akin to passing out, the person is still conscious, but their unconscious defenses have shut down. I think this type of broken is really dark and probably quite eerie to witness. Perhaps one day, I'll get to experience it. But for right now, it's not a goal of mine.