Log 12 Spiritual Tempering
This log is circumspect as I have no way of training this and have very few diverse examples of this concept in action. The thing is that all people in this world have physical and mental energy.
The physical as I mentioned in the past grows with the health and strength of the physical body. The spiritual energy grows through external experiences like studying, meditation, and life experiences.
There is an interesting phenomenon however with the Uchiha clan in their eyes. The eye of a Uchiha will awaken and advance a Kekkei Genkai when sufficiently stressed. This counts as a life experience one can grow from, but why don't eyes advance through studying and meditation if they also advance through the strength of one's Yin energy?
I believe that this is the case because life experiences do not increase the quantity of yin energy but the quality. Quality necessary to activate and use the Sharingan. It is hard to test this theory as how can one test the quality and quantity of one spiritual energy?
I suspect however that the greater the quantity and quality of one's spiritual energy the less a Genjutsu will affect you and the greater the power you can enforce in a Genjutsu. This is likely the case as those who have been known to cast the Strongest Genjutsu had more advanced Sharingan.
No one with a weaker Sharingan has trapped another with a more advanced Sharingan in a Genjutsu. This likely means spiritual energy even before tempering needs to grow to a certain quantity like check points to have an effect.
Is this because a Sharingan eye somehow makes a person's chakra network more durable against a genjutsu? Might it be that the greater the Sharingan the better the spiritual energy and the less effective that weaker spiritual energy has upon it?
Also kids just so you know I suspect the reason why those who have a Sharingan have such good Genjutsu is quality of vision. It allows them to see the world in such crystal clear clarity which would help greatly when creating realistic mental images to ensnare a target.
The other is the power of spiritual energy. If a person has a robust spiritual energy it's hard to break free even if you realize you are in a Genjutsu so a Sharingan represents both key features in the use of Genjutsu.
Eyes are also seen as the windows to the soul. What does that say about the eyes that when you look into them affect you spiritual trapping you in a Genjutsu? When the special abilities unlocked from the eyes are based on the personality (mental/spiritual expression of a person) of the one who awakened the eyes.
This does not mean you need to go through trauma to build a resistance to Genjutsu or increase the power of one's yin. As I mentioned earlier, studying, meditation, and life experiences increase the overall power so as long as you are smart like the Nara clan (Known for powerful yin energy shadow release) or study a lot your yin energy will increase.
All the Chakra concentration exercises in this log book will also build up your yin due to meditation as long as you work hard your yin will increase. If you truly want to temper your spiritual energy then I advise not putting yourself through false Genjutsu of bad things happening to you as it might only temper your mind once due to a subconscious disbelief that the next bad experiences you suffer aren't real causing dissociative disorder
What would be the safest means of tempering is to treat your spiritual energy like a blacksmith tempers metal. Blacksmiths generally use a series of light, softer strikes instead of a few heavy blows. It reduces the risk of warping or cracking due to the localized stress from a single heavy strike.
The idea of stress causing the risk of warping and cracking can be seen in people who are extremely stressed leading them to crack under pressure and commit acts against their usual moral code or to warp and change personalities entirely. This failed tempering is identical to that of people so it is best to take many small and varied strikes of various intensities and styles.
I don't mean for you to commit self-mutilation for power but different subtle means of controlled physical and psychological torture even something like living with itchy clothes can temper your will and spiritual power. Ninjas know a lot more about torture so learning a bit of that can help you but I will write down a few innocuous real-world examples as well as examples that have worked.
Training
Physical
Itching powder in all your clothes, Constant difficult physical training, mild consistent self-harm.
Mental
ugly clothes, being bullied, living with a physical impairment or diseases (itachi), watching or killing loved ones, and surviving traumatic events (quite a few Uchiha).
Footnote: Now that I have talked about the spirit and how to improve it, I am going to have to sit back a moment and think about how I am going to explain nuclear physics and how one could create a nuke with normal chakra natures. Worst case I will just explain how it works to you and you can create it or explain it to a scientist in 20 years.