The Buddha once met a nature hermit who was close to figuring it out, but didn't know what he lacked. He kept watching nature arise and fall (Annica, Impermanence). Watched how nothing ever satisfied his own mind, let alone every being around him (Dukkha, unsatisfactoriness). With this issue, he approached the Buddha.
"Let it be," said the Buddha. "Let the trees be. Let the animals be. Let the mind be. Leave it. Let it be."
With just that teaching, the hermit made the breakthrough and became an Arahant.