Add(sorry iPad post) : Familiarity of the level to be achieved, the timeframe involved, and the ingredients in hand, would determine what missing ingredients are necessary to be obtained or developed, that the recipe for successful achievement of results can be followed...like a cake, one may see what it looks like, know what it is made off, and even, if every household follows the same recipe, it may come out different, some better than some....it is however those who, keep trying, slightly adjusting, slightly changing the combinations, striving for excellence, and learning, would consistently produce the best treat...doh mean they won't miss now and then..