It is from Dē obitū Valentīniānī, § 1. Gratian says: ‘aut [nē … vidērēmur] refugisse incentīvum dolendī,
cum doluisse plērumque sōlātium sit dolentis:
simul cum dē ipsō aut ad ipsum loquor,
tamquam dē præsente vel ad præsentem mihī sermō sit.’ The sentence ‘cum doluisse […]’ is what is causing problems. Liebeschuetz & Hill suggest ‘when to give expression to grief is often a comfort to one who is grief-stricken’, but I arrive at ‘when to have grieved may be for the most part soothing for the one grieving’. What am I missing?