What part does the supernatural play in the duels between Sir Gawain and Sir Launcelot?

The supernatural of the duels between Sir Gawain and Sir Lancelot that take place near the end of Sir Thomas Malory's "Le Morte d'Arthur" are the increase of strength that Sir Gawain experiences between dawn and noontime. This causes Sir Lancelot a lot of difficulty and gave a big advantage to Sir Gawain during their duels. As the exerpt of the book states ""Then had Sir Gawaine such a grace and gift that an holy man had given to him, that every day in the year, from underne till high noon, his might increased those three hours as much as thrice his strength, and that caused Sir Gawaine to win great honour."