If the consistency of your icing is not right, your decorations will not be right either. Just a few drops of liquid can make a great deal of difference in your decorating results. Many factors can affect your icing consistency, such as humidity, temperature, ingredients and equipment. You may need to try using different icing consistencies when decorating to determine what works for you.
As a general guideline, if you are having trouble creating the decorations you want and you feel your icing is too thin, add a little more confectioners’ sugar; if you feel your icing is too thick, add a little more liquid.