Key Insights from C.S Lewis on Suffering and Mental Pain:

• The Nature of Mental Pain: Lewis wrote in A Grief Observed that "mental pain is less dramatic than physical pain, but it is more common and also harder to bear". He added that the obligation to conceal it increases the burden.
• Grief and Fear: He began his exploration of loss by saying, "No one ever told me that grief felt so like fear". He described the experience of immense despair as a "lazy, sneaky, deceitful" feeling that can skew one’s perception.
• Mood is Not Evidence: Lewis often argued that emotions, while valid, do not dictate objective reality, saying "mood is no evidence". He believed that mental health challenges and despair do not mean that God is absent or that the sufferer’s life lacks meaning.
• "The Megaphone" Theory: In The Problem of Pain, he famously stated that "God whispers to us in our pleasures, speaks in our consciences, but shouts in our pains. It is His megaphone to rouse a deaf world".
• No Linear Process: Lewis noted that recovery from severe depression or grief is not linear, but a "spiral". 

His personal writings during bereavement showed a raw, questioning faith, rather than a stoic acceptance, proving he viewed mental anguish as a complex, torturous experience.