In order to manifest succesfully, there are three mental blockages that must be removed, to manifest in the most sufficient and practical way:

1) The ego's need to control

2) The concept of linear time

3) An outside force that manifests for you

These three aspects can easily get in the way of the practical manifestation process.

The Ego's Need To Control 

Letting go of the ego's urge to control is essential, because the ego tends to come up with thoughts and beliefs that are not based on truth. The ego is a master in trapping you to think negatively and not believing in yourself. Remember that the thoughts that are in contradiction with the thoughts that you must have to manifest your desire, are just part of a story that you tell yourself.

A famous quote by the famous American engineer Henry Ford: "Whether you think you can or can't, you are right." It's a powerful statement, because it explains that whatever you believe, is true. If you are negatively influenced by low vibrational thoughts and beliefs, the world will reflect those emotions back in negative circumstances and situations. That is why you must practice letting go of controlling thoughts and possible outcomes through conscious thought observation and not getting swayed or influenced by negative emotions.

Let go of the need to control by setting intentions that implies the manifestation already being fulfilled. That way you can surrender in an optimal direction without disbelief. 

can be done through daily meditation and using exercises to clear negative thinking. Read the article "You Are Not Your Thoughts", as this might benefit when struggling with this type of situation. Keep talking positively and highly of yourself and your desires at all times.

The Concept Of Linear Time

As most people know, "time" is an illusion. Linear time means moving from the past into the future in a straight line. If you were to follow this concept in regards to manifestation, it would mean that whatever you want to manifest, is not being created now, but in the future. This is however false, since we dictate the future by what we think, feel, expect and believe in the present. Nothing is ever really created in the future, because the future doesn't actually exist. The only moment that exists is now, therefore all of manifestation happens now. The vibrations within our energy field at the current moment and our creations within the mind, always create our future outcome.

An Outside Force That Manifests For You

Some believe what we experience is being given or created by an outside force, like a God or other gods or godessess. It's a topic that could endlessly be up for discussion, for whether this is true or false. Quantum physics science has shown that whatever we experience, is created by the human imagination, which is called "God" in scripture.

The imagination or awareness is referred to "God " in the Bible. The Bible could lead as a manifestation guidance to life. We can test that the imagination creates reality, by impressing a same exact scene onto the subconscious mind by repetition. That exact scene will ultimately be pushed out into our reality.