Simply put, thoughts without feelings and pictures are just much weaker and not very effective. If you add a picture to your thoughts, these thoughts become much more powerful.
If you think of spirit being at one end of the spectrum and matter at the other, than what you are doing here is working from cause (thought) to effect ( manifested desire), from beginning to end. Visualization is life in the process of taking form. Everything that exists is thought solidified.
You may want to pursue the scientific explanations of the creative process, by reading a wonderful book, 'Your Invisible Power' written by Genevieve Behrend.
You must start to see yourself as the person you want to be, and having what it is you desire. In other words you want to place yourself in vibrational harmony with what you desire. Like energy attracts like energy.
We all posses more power than we recognize and much more power than we use. Visualization is one of these powers.
So how can you visualize effectively?
When starting to visualize, past results do not predict your future therefore, simply let them go.
You must continuously use your will to inhibit every thought and feeling that is contrary to your desired picture. It is important that your will be strong and not be shifting back and forth from what is desired to what is not desired.
Yet, one of the tricks to visualizing is to do so without anxiety or strain. Practice your visualization in a confident and relaxed manner, while maintaining the expectation that the desire will manifest.
Many people fall into the trap when visualizing of believing that their results are contingent on conditions or persons. Suffice to say that such a belief will delay your results or create imperfect results. Do not worry about the "How", in other words how the result will come about. Simply focus on what you desire. Also, do not concern yourself with what others might be thinking or visualizing.
A fun way to start your positive thinking visualization exercise is to create a dream board of what you desire.
Take the time to cut out pictures that represent for you the freedom, the joy, the love, and the satisfaction you are longing for. Glue these pictures on a board and hang this board where you can see it frequently. Or, keep a photo album and every day look at these pictures and impress them upon your mind.
Next, take a few minutes daily to sit quietly and run these pictures of your desired results in your head. Add movement to your pictures and run it like a movie. Feel the feelings that you will enjoy when this plays out in physical form.
Now we must get clear on one thing. Visualizing is extremely powerful however, if you sit on a couch all day and simply visualize that will not get you anywhere.