How important is it to concentrate on positive ideas and not to think on negative things! In Vol. IV of the Sufi Message Hazrat Inayat Khan says:
“When a person begins to think he is under an unlucky star, with everything that happens, good or bad, he will think: “It all brings bad luck to me. From everywhere bad luck seems to be coming”. Even a good thing that person will believe to be bad, because he is looking at it in that way. And when a person is living in the thought that good luck is coming to him, everything that comes is in the form of good luck.
The more we study this question, the more we find that our mind is the master of life; and we become the possessor of the Kingdom of God as soon as we have realized the power of thought and concentration upon our life. It is because of the absence of such knowledge that one does not value that divine spark which is in oneself; and by being unconscious of it one goes down and down, till one reaches the deepest depths. No sooner has one realized this than one begins to respect oneself; and it is the self-respecting person who has respect for another, it is the one who helps himself who will help another, it is the one who can raise himself who will take another person also towards the heights”. Sufi Message Volume 4, Healing And The Mind World, Part 1, Health, 11. Imagination