The old "fear of completion" theory is one more thing that Charles Higham needs to be kicked in the nuts for. Welles had a self-destructive streak in him, there's no doubt of that, but I think the whole fear of completion thing is overblown. Welles' problem is that he worked in a very public, very commercial medium, a medium that places a premium importance on getting a product finished and getting money out of it, as soon as possible. But Welles didn't work this way for much of the latter period of his career. He paid for his own projects, and if he completed them, fine, and if he didn't, then he either moved on or continued trying to complete it if it truly meant something to him and if he had the wherewithal to do so.
In the end, I think the whole "fear of completion" theory boils down to a couple things: expectations of Welles, and expectations of movies and the way they are made. With someone like Welles, audiences expected great things, and he delivered as best he could. When left to his own devices to make movies, as he often was after 1968 or so, he obviously felt no compunction to rush a product to cinemas. When Welles had a reasonable amount of funding, he produced a completed feature. He didn't have "fear of completion" when he had the proper backing, did he? The financial power behind a picture may not have liked it and chopped the film up, but you can't say Welles got cold feet and bailed before the film was done. A minor case could be made for Arkadin, as it was pulled out of his hands due his missing a deadline for editing, but were Touch of Evil, The Trial, Chimes at Midnight, The Immortal Story, and F for Fake left incomplete for others to patch together from scraps? If Welles took his time making Don Quixote or anything else he financed himself, do you blame him?
A writer can toss a bad draft of a novel, or move on to something else if he loses interest, or it fails to live up to what was intended, or what have you. The filmmaker, working in a medium so visible and expensive and involving so many other people, cannot. In the end, doesn't this reputation rest, really, on the failure to finish Quixote and The Deep? How many of the others can he really, seriously be blamed for not finishing in a "timely" manner, free of circumstances beyond his control, and which were risks of the way he worked, ie independently?