KaraC: No actually you bring up two good points. Sirius's death closed a window for him that he thinks can never be re-opened. Of course time will tell on that score.

Also, there was a time at Hogwarts when Harry felt that he truly belonged for the first time in his life. He expected to always belong, sharing experiences with his friends. Now, however, he knows his destiny doesn't include his friends. Once again, Harry feels that he's alone with a burden that no one can share. Just like in the muggle world, Harry is on the outside looking in. Tough way to go for our hero.