You need to fight minor enemies outside of the temple first to level up. Also, you need the shield spell from the first town. If you do that, the darknut poses a significantly smaller problem. It doesn't get easy by any means, but it's possible to defeat him. If not, you need to go outside and...
James Rolfe's review of Adventures of Link.
Warning. Contains strong language and infantile humor. But his main point stands. A hard game isn't bad in itself. But it's the sudden jump in difficulty after the first level - combined with a shortage of extra-lives and the fact that you always have...