...just like people can be «brain-washed» into becoming «insane» and «irrational» people can also learn how to «mind-control» /themselves/ via processes like self-hypnosis; the CHOICE, how-ever, remains up to the metaphoric «Neo» within you; whether you CHOOSE to «download this software» (accept the words here that I provide) into your metaphoric Operating System (i.e.: Mind) remains your free-will-choice; the Matrix movie was known to present a «choice» of either a Blue or a Red Pill...
Some people have problems/issues with negative-influences, such as addictions to substances, and, clearly, cause people to become prone to negative-thoughts, negative-emotions, etc.; consider how «irrational/insane» some (or many) people get when they are «drunk» or «under the influence» of some substance or another... they have essentially «lost control» of their thoughts, their feelings, their actions, if you've ever had dialogue/conversation with an «addict» before, they will often tell you how the «substance» (that is harmful to their own body) is _always_ on their «mind» (and, thus, also harmful to the «mind» itself).
Food-Choices are also quite relevant. See the comments-section from this video...?
Some of them have parents talking about how the other parents can't figure out why their own children are so well-behaved compared to the «wondering» parents; it turns out that what you eat also affects your mind, your mood, your emotions, and, thus, ultimately, your health... then we can also get into the works of Dr. Masuru Emoto who demonstrated that negative-energy continues to linger on within liquids/substances that have been exposed to negativity (sort of like «haunting» phenomena) and, for those of you who aren't pseudo-skeptics, you can just imagine what would happen if you were to consume a bunch of «cursed (and/or haunted)» (filled with negative-energy) substances/foods/etc.
Controlling your own MIND is the MOST-IMPORTANT aspect of _being_ an ISBE...;
Take time to set aside to do relaxed deep-breathing meditation, meditation, meditation.
Learning the Star Prayer and using it thrice (three [3] times) a day can also be useful...
http://www.the-testament-of-truth.com/truth/web/starpray.htm