Russel argued that (LUST aside) the six affect streams were related across (potentially) vagal tone. She saw that the CARE and PANIC affects were of the same kind, namely, affects that function for connection. Likewise, she saw the PLAY and ANGER affects as related, as well as the SEEKING and FEAR affects. She identified PLAY/ANGER as “mastery” affects because it is the way we learn skills; and she called the SEEKING/ FEAR stream as “tremulous” energies because of how we “tremble” in excitement at the boundary of seeking and fear.
– https://bonnittaroy.substack.com/p/the-affect-streams