"The world is an illusion"
To handle illusions with skill is to penetrate them.
Here is a practical tool, a simple meditation method. ◦Transcendental Meditation. There is much research surrounding it.
"A little learning is a dangerous thing," according to the English poet Alexander Pope (1688–1744). All teachings in the world are not first-class teachings. For example, when someone tells the world is an illusion, kindly ask how it can be so. what is the value of such a teaching in the said illusory world.
Param(a)hansa Yogananda (1893-–1952) and his claims that the world is unreal, illusory, a dream, would all be his illusions if so. Yes, he painted himself mentally into a corner thereby. By contrast, decent teachings put lots of persons on a nice path to walk along. They also warn against associating with fools. Buddha does. [Apannaka Sutta]
But there is more to the illusion teachings. The Bhagavad Gita 16:7 and onwards tells
demoniac . . . say that this world is unreal [and] rise as the enemies of the world . . . deluded. (Excerpts from Srila Prabhupada's Bhagavad Gita As It Is, 16. 6-16)
The Bhagavad Gita on demons and their works (chap. 16) may put illusion teachings in a proper perspective. For example, there is a commentary on the Bhagavad Gita published by Self-Realization Fellowship. Yogananda comments at length on many verses, but passes by the Gita verses that define demoniacs [asuras], without any comments. However, he repeatedly told the world is not real [Quotations] . . . (Yogananda 1999:974-75)
Somehow the one who said the world is unreal, produced a Gita commentary without emphasising in the least how he was a demoniac, an illusory author, an illusory demon or a demon of illusions. A caveat is needed, though: A translation derives in part from the orientations and repertoire of the translator. Many Sanskrit terms have several meanings, nuances of meaning, and connotations and are often translated a bit differently. A good Sanskrit-English Dictionary is a boon. John Grimes has written A Concise Dictionary of Indian Philosophy (3rd ed., 2009). There are many others around too.
The Sanskrit asatyam in verse 8 can mean "without truth", "without reality" (unreal, illusory) The Sanskrit Dictionary for Spoken Sanskrit has "false, lie, lying, untrue, falsehood, untruth". Also note what meanings an established tradition (or school) usually chooses in the matter.
"Those who teach that the world is unreal are demons and like to harm people," can be a very significant translation.
The demonic know not the right path of action . . . They lack purity and truth and proper conduct. (7)
They say: "The world has no moral foundation, no abiding truth . . . (8)
[They] commit many atrocities [extremely wicked or cruel acts]. They are enemies of the world, bent on its destruction. (9)
. . . they strive . . . by amassing wealth dishonestly. (12)
. . . they sink into a foul hell. (15, 16)
(Yogananda (and SRF). The Yoga of the Bhagavad Gita (2007, 16:7-16, excerpts)
Those things that I have known with direct knowledge but have not taught are far more numerous [than what I have taught]. And why haven't I taught them? Because they do not lead to to calm, to direct knowledge, to self-awakening.
"And what have I taught? The path of practice leading to the cessation of dukka (suffering, stress, etc). [More]
The hub of Buddha's benign all-round way "on and up" in life is meditation. Moral and sound ways and dealings go into it too. [More]
Essentials of yoga training can also help some. And among researched meditation methods, the most helpful is Transcendental Meditation. [◦Research findings]