Spank me too hard....I get tough.
Spank me too fast......I get tense.
Spank me too lightly.....I get frustrated.
Noticing a pattern here? Yup, no tears. The idea of being spanked so hard or fast that I start to cry is a really appealing fantasy to me. In practice, it doesn't happen. Ever.
This may be a little too much information for safety.....but I trust you.
The only thing that makes me cry is when I have done something genuinely bad, a punishment is made inescapable, I have to face my fault head on and pay the price for it and (crucially) the tone of the punishment is, "I'm doing this because you did XYZ thing and I care enough for you to not allow you to get away with it." Ouch.
I think it's the combination of my own regret and the application of punishment by a caring but implacable other. In the past it has usually involved a very long spanking (usually with hands and other implements) in a physically close position (OTK basically).
For me, crying is a manifestation of the deepest and most complete form of submission I am capable of. In 20 years of TTWD, it's happened maybe four or five times.
In summmary - yup, it's definitely emotional rather than physical for me.