Enabling psi requires that a person be mature in their judgements, secure in themselves, and able to handle a great amount of responsibility. While it is true that psi is available to everyone to develop only those individuals that make the effort towards true oneness and life change will see the ultimate outcomes of psi. Psi will develop for anyone that chooses to learn the techniques, but if self-betterment is not actualized than a person will see their abilities plateau. Abilities plateau when development of the self hasn't progressed enough to allow an individual to understand a necessary concept and without understanding there is no power to continue ability growth.
The most common growth plateau is caused by responsibility. A person must be able to take responsibility for their actions and all subsequent consequences. A person must also take appropriate responsibility for their interactions, especially those caused by energy. Unfortunately responsibility is rarely stressed in importance and so people do not bother to learn it since there is always someone else to take the blame. In taking responsibility a person is able to admit to having a part in situations they are involved with. Once a person admits their responsibility they have the truth of their interactions and are able to gain the power to further develop themselves. Of course, married with the concept of responsibility is the need to understand that what happens within a person's reality is almost completely up to them.
Personal understanding and growth starts with choices made in reality every moment and if the majority of choices point towards self-betterment than a person's life and psi will continually grow.