How does The Secret pertain to Yoga? For those that haven't seen this DVD, it's about the Law of Attraction which states that "what you put out, you get back." Ancient idea in new packaging. A bit too much hype for my personal taste, but kudos to the creator, Rhonda Byrne, for finding a way to get this "philosophy" out to so many.
John Friend of Anusara Yoga talks about attitude being the most important aspect of our practice. The other main aspects being alignment and action. The Secret is basically saying the same thing, and much more. If our attitude is negative, our results are negative. The flip side, is that with a positive attitude you gain positive results. This is not a new idea. Even Jesus and Buddha talked about this. "The kingdom of God is within you." "All that we are is the result of what we have thought. The mind is everything. What we think we become."
A big part of a Hatha Yoga practice is being intimately aware of yourself. Not just your body, but your mind and thoughts. You can use the knowledge found in The Secret (and countless other books or on Oprah, for that matter :-)) along with the awareness found in a Yoga practice to bring more joy and fulfillment to every day.