Busy

I find your suggestion a bit difficult because there is a difference between being careless, where it is clear that it is negligence, and being preoccupied. Being careless is not paying attention to the law, and there it is understood that the person is required to be alert and pay attention to the laws relevant to the situations in which he finds himself, but with regard to being preoccupied, it seems to me unreasonable to require the person to be constantly alert to every detail of his life.

The question of what is between being careless and being careless is a very difficult one, and the commentators are very confused about it. But there is also a dimension of negligence in being careless. You walk near plants on Shabbat and can pluck some from them as you walk. Of course, you can also be careful if you are aware. This is not constant alertness for every detail in your life, but caution in the laws of Shabbat in a certain place and time when there is a fear of prohibition. Not bad at all. But as mentioned, I am inclined to the opinion that it is truly permissible.

Clarification note: Contrary to what you say, negligence is also a failure to pay attention to reality, not just to the law. See Mishnat Shabbat p’ a great rule.

Regarding your confusion about Ra'a, it seems to me that this issue can be clarified with the help of one of the investigations of the deciphering of the code in the Responsorial Psalm. It investigates and attempts to clarify from the words of Chazal whether mitzvot must be performed or whether they will be performed. Similarly, regarding the desecration of Shabbat, is the desecration determined according to the person for whom the situation is completely permissible and he has no problem with it, or is there a fundamental problem with the act itself, a problem that may throw a consequence back at the person himself.

These investigations always seem dubious to me. Certainly in a blanket statement. But in any case, it's about a rabbinic prohibition, so it doesn't seem relevant to me.

First, Reka himself distinguishes between the laws of Shabbat and other prohibitions, stating that on Shabbat there is no prohibition when one is engaged in the work of thinking, since the Torah forbids it.
Secondly, the explanation is very simple: even if the man did not commit a transgression, in this case he violated the hafza of isura (and even though, according to the rabbi, Epicurus does not transgress the prohibitions, here it has the meaning of a prohibition)

Here it is clear that he did not violate the purpose of the prohibition because according to the Torah it is permitted. The whole discussion is why the Sages created an additional layer.

Continued: The fact that something is considered a forbidden object in other places does not mean that it is also considered a forbidden object on Shabbat, but that it is not obligatory, and this is because the reason it is not transgressed on Shabbat is that Shabbat prohibitions are fundamentally different and it is not appropriate for something to be considered a forbidden object on Shabbat.