The mind has two invisible parts i.e conscious and the subconscious. While the conscious mind reacts in real-time, the subconscious is a much powerful section of the brain which needs to be trained properly.
To understand these two terms in live example, you can imagine someone trying to learn driving a cycle or car. Although he is consciously active but despite that being a new-learner he will have hard time balancing or driving straight.
A person who has trained subconscious at an expert level, will be able to drive even while talking to someone on passenger seat or listening to songs. It is his subconscious doing the driving part. The conscious mind kicks in when there is any threat or obstruction on the road which needs immediate attention.
This is why even those who are drunk drivers can drive perfectly for miles (since they have trained their subconscious in the past) but have high chances of meeting an accident if there is any major obstruction or some danger which requires your immediate attention. An expert drunk driver might have his subconscious trained perfectly, but the flaw in conscious mind could have deadly consequences.
Now, subconscious mind is said to be 30,000 times more powerful than conscious mind. So by training your subconscious mind through visualization techniques you can train your mind to achieve anything in life.
Watch Video to understand this whole concept of Visualization by Swami Mukananda.