Once upon a time there was a woman who liked to knit. She had been knitting for years, but carefully avoided any patterns that were not rated "beginner" or "easy". She loved the look of more complex patterns, but was afraid she might make mistakes or get in over her head. She always used cheap yarn because she didn't want to "waste the good stuff on my level of knitting". Her Fairy Knitmother tried to encourage here to branch out, but she was too afraid of making mistakes.
So one night her Fairy Knitmother found several patterns she knew this woman liked, but was afraid to try, and with a touch of her magic wand changed the difficulty level on them to "easy" and the required yarns to higher quality. The next morning the woman found these patterns and was delighted. "At last", she said, "patterns I like that are at my skill level." And she began to knit.
She made a cabled sweater, a Fair Isle hat, and slip-stitch mittens. They were beautiful, and she was so proud of them. There was a small mistake in each one, but no one but the woman who knitted these items could find the mistake, and since the patterns were rated "easy", she was not worried about these mistakes. She gave the cabled sweater and Fair Isle hat and slip-stitch mittens to her loved ones, and they were thrilled.
Then the Fairy Knitmother told the woman the truth about the skill level of the patterns. "You see," said the Fairy Knitmother, "you only thought you couldn't do these patterns. You can do anything if you believe you can."
"But there are mistakes in them!" cried the woman.
"Of course there are, my dear," responded the Fairy Knitmother. "The only people who don't make mistakes are people who aren't doing anything."
The moral of the story is: believe in yourself. You can do anything you want to do if you believe in yourself. If you want to knit with silk yarn, do it - life is too short to knit with cheap yarn. If you want to try a more complex pattern, do it. You might surprise yourself with how well it comes out.