The garden washed away the warmth of my heart; otherwise, the lightning would burn my nest.

This profound couplet speaks of emotional survival. The poet suggests that the harsh reality of captivity (or trauma) has forced him to dampen his intense passion. If he hadn't cooled his heart's fire, the sudden shock of life's storms—the 'lightning'—would have utterly destroyed his fragile peace and home. It's a beautiful reflection on how emotional self-preservation is sometimes a necessity for survival.