Most teachings warn about opening yourself up to the inner levels through meditation without being closely connected to some developed teacher and their past teachers. This is because of the Jinns (Non-human spirits).
Jinns were previous to humans on the earth. When humans were 'quickened' the Jinns were no longer able to come into bodies to develop. Those based in the physical and etheric simply quietly faded away (as humans on that level do after death) but those past the 2nd initiation continued to exist on the astral and etheric levels. They manifest on the etheric levels, returning to the astral when they die. They play with the human race on the etheric level, through peoples negative emotions. Their main chance for progress being to replace some failing human soul in a body. Then they shift to the human line of development and forget their previous existence as a Jinn.
The most powerful Jinns are on the upper levels of the astral while the least powerful are on the lower levels. Most esoteric teachings recognize their existence and give them some respect without getting involved with them. The Jinns range from reasonably positive to quite negative - just as humans do. They have some sort of organised society.
Normal humans suffer from their influence and usually only a persons guide protects them. If you harbour negative emotions then the guide cannot prevent access to the Jinns through that negativity. If you insist on 'opening yourself up to the inner worlds' through quiet concentration, as some psychics deliberately practice, some foolish teachers teach and some innocent students follow, then the guide is powerless to protect you. It is better to first refine and strengthen yourself internally. Then at a later time the intelligence developed on each of those levels, will gradually, with its own timing, naturally spread beyond yourself into the inner worlds on that same level.
My teacher Abdullah told me that about 20 of his students were well under the influence of the Jinns. Abdullah would send out light to that person daily, but if the person persisted with the negative states that were allowing access to the Jinns, then he would withdraw his help after a year. At that point he stated, the person 'was stuffed' (without much hope). He worked this way because he said the Jinns were also beings who deserved their chance at future progress.
Looking for psychic powers, including the foreseeing of the future, attracts the attention of the Jinns. Having existed on the Earth for 10's of thousands of years within the Etheric realm, they have more experience there than even developed teachers. They can enhance any persons attempt to gain power on these levels and can predict with great accuracy the future course of events on the earth, passing that information on to whoever looks for it. To accept their help (usually unknowingly) is the beginning of a slippery slope under their influence, which begins with an early increase of power and ends with distortion and diminishing energy once well within their grasp. Students are often impressed by such abilities of a 'teacher' - who typically has not undergone long hard training to refine their inner nature with some past teacher who has themselves passed through the same process with their teacher.
Many years ago one of my friends bought an old house but when he went to renovate and live there many strange things happened. Noises, closing doors, objects flying around the rooms. He was told by his teacher that it was a powerful Jinn (usually they have no power in the physical world) who lived there and was trying to chase him out. He was advised to send his family away but stay himself, play tapes of chanting of mantrams, repeat a mantra constantly himself and keep a determined will that it was his house and the Jinn must go. After 1 week all strange activity ceased and never returned.
With the development of Human#4 (past 3rd initiation) a person is more than equal to the stronger Jinns, but may still suffer their influence. The Jinns main chance with such a developed person is to tempt them with power. Numerous are the examples of developed people who begin by believing they are the most developed person in the world, then progress to believing they are the world saviour. This is a sure sign of influence from the Jinns and will certainly block all inner progress in a Human#4. If this happens at an earlier stage, then that person may be lost to the Jinn.
After the 4th initiation (Human#5) a person's field of activity moves from the deepemotional (astral) to the deepmental (celestial), while their being is centred on the 4th energy level. Then that person is beyond the influence of the Jinns. At that stage they may choose to help the Jinns as part of the complex life of the solar system.