The main reason that it is difficult to use miracles is because of interference. Interference occurs when one is not willing to give up their own interpretation of how the miracle should work. In other words, they believe they have access to information that will allow them to control the outcome a miracle would bring. This will prevent the miracle from doing what is asked of it.
Once the miracle has a direction, it takes into consideration everything to make sure everyone wins. There is not anyone on the Planet Earth that has access to the kind of information that would allow everyone to win.
Once again, it is just like learning to use a computer. There are things that can be done on a computer, and things that cannot be done. Attempting to make a computer do something it is not programmed to do will disrupt the outcome. Correction must be applied so the computer can be used correctly. The same is true of miracles. When interference has occurred, and you will know because things are not running smoothly in your external world, correction must occur.
In the beginning, the correction that must occur is to stay out of the results. Everything that you need for your miracle to occur will be provided, but you must learn how to stay out of it.