Question

For years, Arthur had treated the old family archives as a dusty mausoleum, a place where history lay inert under blankets of gray lint. But as he began untangling the letters of his great-grandmother, he realized the collection was not a tomb but a greenhouse. The fragile yellowed pages, far from being dead remnants of the past, were actually root systems feeding his own sense of identity. Every ink-stained description of the dry prairie winds or the early autumn frosts served to tether his drifting ambitions. Whenever the chaotic demands of his modern career threatened to sweep him into a state of perpetual anxiety, reading these letters anchored his thoughts. It was as if the written words of those who had survived before him provided a heavy ballast, ensuring he would not be carried away by the passing gales of temporary hardships. He sat at the mahogany desk, tracing the fading cursive, and felt a sudden stillness. The ambient noise of the city outside seemed to fade, replaced by a quiet assurance that his current struggles were merely chapters in a much larger, ongoing narrative.

As it is used in the passage, the metaphorical phrase 'anchored his thoughts' most nearly means that reading the letters had which of the following effects?