Letting Go of Intention

I have been trying to manifest my desires and getting nowhere.   I have always believed in positive thinking and last year read the law of attraction and thought that took positive thinking a step further.   I can’t get it to work for me.   I have tried to keep my thoughts on what I am trying to manifest and not be discouraged because it is not happening.   Then I discovered your web site and now one of your books “The Book of Secrets” and you believe in ‘letting go’.   I just don’t get this.  I am trying to manifest my desires by keeping my intention clear and foremost in my mind.   If I let it go and give it up to the Universe, have I not just given up on my desires?   I can’t connect this to concepts in my mind and I don’t know how to let go.   Can you clarify this for me?