One interesting idea presented there is that oneg (pleasure) & nega (plague) comprise the same letters, just in a different order.
oneg/ענג — nega/נגע
Rav Schwartz quotes Sefer Yetzirah, noting that nothing is higher than oneg while nothing is lower than nega.
This is because oneg, when used positively, can lead us to great heights.
As we know, a wealth of Torah scholarship exists which emphasizes the great pleasure of being close to Hashem.
This is why very high-level tzaddikim are happy all the time—they're always with Hashem & basking in that pleasure.
However, within corrupted oneg lies the source of all bad middot.
Oneg, which can be found at the highest levels of kedushah (holiness) also "has the potential to deteriorate into destructive nega."
I found that interesting in light of the nega coursing through the world right now.
Interestingly, we hear about the covid-19 nega (which isn't a plague like the Spanish flu or Black Plague—plagues which killed most of their victims, sometimes within hours—but covid-19 causes disruptions anyway) mostly in places with advanced technology.
And advanced technology provides unending opportunities for destructive oneg.
Like, how much have you heard about covid-19 in undeveloped areas of the world? Initially, cluster maps showed almost nothing throughout the undeveloped areas of the world with large cluster zones in America & Europe. But even now, how much do you hear about covid-19 in undeveloped areas?
And as stressful as modern life often is, there is also a huge emphasis on leisure activities.
An "eat, drink, be merry" attitude permeates Western culture.
To use oneg properly, it must be used for positive connection.
Social media & comment sections often facilitate comments meant to hurt, criticize, or mock.
The authors of these comments often enjoy what they're doing—an example of destructive oneg for personal pleasure.
Likewise, many reality shows manipulate situations to humiliate or sabotage the participants—all the while making it look spontaneous.
With today's undeletable videos, the humiliation never ends. Sometimes the victim receives millions of jeering comments, plus harassment in real life.
Another example is how one reality show meant to improve restaurants—but actually invented over 60% of the problems "discovered" on the show. As a result, these restaurants often went out of business.
So we see a modern plague of humiliating & sabotaging other people (including ending their livelihood)—all for the purpose of base "entertainment" (a truly low-down level of oneg) and providing fame & money (more lowly oneg) for the callous producers.
This is the diametric opposite of oneg for connection.
It's destructive oneg.
Eating delicious food can connect to you Hashem by making a heartfelt blessing over the food, then eating it with gratitude & and the intent to keep yourself healthy for doing more mitzvot.
It can connect you to the person who made the food by increasing your appreciation of & gratitude toward that person.
That's oneg for holy connection.
However, one who eats merely to enjoy the physical act of eating (especially when indulging junk food without even being hungry) uses oneg purely for personal pleasure—and that deteriorates the sublime purpose of oneg.
Rav Schwartz notes this idea has wide application, including in relationships, especially in marriage.
When people look for their own personal pleasure, rather than connection, the relationship eventually disintegrates because it was only ever based on what personal pleasure one could extract from it, and not a true bond with the other person.
As Rav Schwartz states on page 102:
Pleasure as a goal in itself is the root of destruction (churban),
but if the goal is to forge connection, it is the root of constructive growth (binyan).