The Loop

 When a person, feeling or an event penetrates deep into the unconscious mind, it becomes too difficult to erase it from there. The unconscious mind consists of the processes in the mind which occur automatically and are not available to introspection, and include thought processes, memories, interests, and motivations.

It's a natural phenomena that many times we keep on thinking about a person, feeling or an event that strikes our mind or inspires us. Whatever we think deeply throughout the day, chances are that it gets converted into a dream and we see it during our sleep. It is obvious that we hardly forget a dream in which we see something emotional relating to our special ones. That dream takes us back to the memories and again reaches into our unconscious mind. It becomes like a loop in our unconscious mind, automatic thoughts -> unconscious mind -> dreams -> automatic thoughts and so on. This endless loop never allows us to forget about that person, feeling or event. 

Thus the unconscious mind can be seen as the source of dreams and automatic thoughts to this loop. It happens without any apparent cause. We always feel them around and when they come in front of us, we behave like they were never away from us. This may be the reason we say it as 'dream come true' when we meet our special ones who stay in our unconscious mind.