You should have a strong desire but not to the point where you get frustrated when it does not show up on time. The desire should keep you excited about life but at the same time detachment will help you stay relaxed and focused on your day to day activites rather than looking for results and wondering when your prayers will be answered. As you have mentioned, if you dont practice detachment then you will bring up the feeling of lack and not having it now.
I like to quote Wayne Dyer when it comes to detachment. Check this out
Success.com : Infinite Patience Produces Immediate Results
Hope that helps.
