As autumn progressed, Egil grew very melancholy and would often sit down with his head bowed into his cloak.
Once, Arinbjorn went to him and asked what was causing his melancholy: "Even though you have suffered a great loss with your brother's death, the manly thing to do is bear it well. One man lives after another's death. What poetry have you been composing? Let me hear some."
Now that's a man who understands melancholic personalities! :-D
Actually, it has been suggested that Egil suffered from Paget's disease. The saga says he had exceptionally broad bone structure in his head, disturbingly mobile eyebrows, and was generally in a bad mood. Also, Paget's disease would have given him a low-level headache all the time, as well as another unusual characteristic, useful to a Viking: when a farmer dug up his skull a century or so ago, the bone did not chip or shatter or break when he hit it with an axe, it just turned whiter.
The saga writer obviously had no access to the science that would have explained Egil's condition, but he did have access to a more general explanation: human nature, something the saga writers seemed very good at analyzing.