(condensed from Ein Ayah, Shabbat 1:88)

Gemara: [The mishna says that in the area of the Beit Hamikdash in which the kohanim warmed themselves, it was permitted to put wood on the fire until closer to Shabbat than it is in one’s home. The reason this is permitted is that] kohanim are diligent.

Ein Ayah: One whose emotions increase to the point that his intellect becomes confused is liable to not remember clearly enough what his restrictions are according to the divinely ordained Torah laws. A person who is susceptible to such a problem must be very careful at the time of his increased emotion that he not violate Torah law, which would "breach gaps into the fences of the world."
The situation could even exist whereby his power of imagination might tell him, in his emotional state, that he is in the midst of activity for purposes of love of Hashem and His glory, [and therefore he should not be unduly restricted]. However, this is a warped approach. It is a foundation of the Torah that the intellect must always be in the superior position and always push one in the direction that it sees as fit based on the Torah and on wisdom.
Kohanim are people who are able to combine these elements properly. They are expected to move away from cold intellectual service of Hashem and embrace emotional elements of their service in the Beit Hamikdash. They energize the powers that could otherwise cool off due to the effect of an abundance of calculations and knowledge on the powers of the body. It is problematic when emotion, which is also a power of the body, is not sufficiently involved. The proper situation is that emotion is involved and the intellect is supervising, making sure that everything is operating to the appropriate degree, which is set according to a certain system and calculation. Even then, the intellect must be present and ensure that there is no longer a need for some type of restraint to prevent even a small infraction against the precepts of the Torah.
The above is a good lesson for all those who feel a need to increase the emotional element of their service of Hashem and thus broaden their spiritual attainments. Their path should be arranged, from the outset, on the path of Torah, which is the loftiest wisdom and contains the proper measuring tools for all of man’s actions. With that in hand, people will succeed in ensuring that the extra elements of emotionalism will remain a blessing. It is not only the kohanim, sons of Aharon, who knew how to be diligent and careful. It can and should be the legacy of the entire "kingdom of kohanim" ( Bnei Yisrael - see Shemot 19:6), whose members shall lead their lives according to the intellect. This is appropriate for a kingdom, which needs to follow wise guidelines in an exact manner, and a "holy nation" (ibid.), which is elevated with intellectual riches and feelings of sanctity, which is the "fire of holiness" (see Devarim 33:2).

With this, we have completed our study of Ein Ayah on the first perek of Shabbat.