Manifestation works on the principles of the Law of Attraction (LOA), one of the most powerful, yet one of the least understood laws of nature. If you are skeptical of concepts like the law of attraction and manifestation of desires, you need to go through an experience to be cured of your skepticism. And to have an experience, you need to experiment. This means you have to make an attempt and check whether this law really works.
If you have to experience the power of the law of attraction, you have to believe in this law. A skeptic will never get success by using the LOA because the primary condition for this law to work is the existence of belief. This is why skeptics keep demanding proofs but never get them unless they are going to accept the experiences of other people.
I am a skeptic myself but I believe in the LOA. Am I contradicting myself? No. The reason I like this law is that it creates a lot of positive thinking. Whether this law works or not, people believing in this law begin to believe that good things are going to happen to them. This belief makes them expect good things and feel good about themselves.
Consider the positive energy generated by these beliefs. It has been widely accepted both by clinical and by social psychologists that positive thinking makes people more energetic and enables them to perform better. People who do things expecting a positive outcome will turn out much better performances than those who are pessimistic of the results of their efforts.
When a person believes in the efficacy of the law of attraction and does things with enthusiasm and positive expectation of his dreams manifesting into realities, he becomes an asset to the society because he will be able to contribute much better, working from a state of expectation, faith and confidence.
The flip side of believing in the manifestation miracle is the disappointment and frustration that might result from the failure to get results, But people who believe in the law of attraction generally convince themselves that failures are temporary and that their faith will eventually lead them towards success.
I am not suggesting that rational thinking is bad. Nothing can be more valuable than the ability to think rationally and clearly. But I am only pointing out that ideas like the law of attraction, the belief that one can manifest his desires etc. also have their advantages.