Facilis descensus Averno: noctes atque dies patet atvi ianua Ditis; sed revocare gradum superasque evadere ad auras – Hoc opus, hic labor est. 

“Easy is the descent into hell, for the door to the underworld lies open both day and night. But to retrace the path; to come out again to the sweet air of heaven – there is the task, there is the burden.”

The Aeneid