The mariner must travel from land to land and teach others, by using his own story as an example, to love and respect everything God has made. At the end, he tells the wedding guest,
Farewell, farewell! but this I tell
To thee, thou Wedding-Guest!
He prayeth well, who loveth well
Both man and bird and beast.
He prayeth best, who loveth best
All things both great and small;
For the dear God who loveth us
He made and loveth all.
The Mariner, whose eye is bright,
Whose beard with age is hoar,
Is gone: and now the Wedding-Guest
Turned from the bridegroom's door.
He went like one that hath been stunned,
And is of sense forlorn:
A sadder and a wiser man,
He rose the morrow morn.
The mariner leaves a great impact on the wedding guest with his story. He's successful because when the wedding guest wakes the next morning, he's wiser as well as sadder for having heard the mariner's story.
The mariner is now a preacher, an apostle. His final penance is to teach his fables and spread his wisdom. He warns others how they can avoid his depression and how to keep away from his path hell. The mariner has to tell people to respect all of god’s creations and not to take nature for granted. The mariner will have to preach his story for eternity if even if his encumbrance persistently returns.