Trumpeter George Recker used to say, “If you can’t sing it, you can’t play it.” It’s great advice. Here’s some similar great advice about singing and playing a horn, as well as several other great practice suggestions from Ted Nash, one of the great players (they’re all great) in the Jazz at Lincoln Center Orchestra.
In the following video, Mr. Nash mentions The War of Art, by Steven Pressfield. Get a copy by clicking on the image.
The Practice of Practice 