Best not to spend too much time diagnosing the 'cause.'
The main DB principles apply in both situations anyway - GAL, 180s, detach, friendly like a neighbour etc....I would keep your focus on you, and on these. You may also want to revisit the chapters on infidelity and MLC in DR.
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus