For me it is trust and understanding.
Trust because we all know the moves could injure us if we don't tap. So we need to know that our partner doesn't want to hurt us and will stop/slow down even if we aren't tapping. Sometimes we don't know the move so having trust in your partner who does, can keep you from getting injured.
Understanding is huge too. Sometimes we just want to work on something even though our partner really just wants to spar. Sometimes we are slightly injured or maybe we are preparing for a special event. When our partner is understanding they will work with you because they know at some point they will be on the other side and need the same from us.
Bonus for creative/curious partners. Sometimes this is the best way to find a new favorite move!
Replied on What makes a good training partner?(c...
25 Mar 11:53
Matching intensity is another good one!