Note: The selections below are all taken from Maggid Meisharim, Rabbi Caro's recording of the teachings he heard from his angelic mentor. (For further information: Rabbi Yosef Caro's works )
The Importance of Mishna
When Rabbi Yosef Caro's angelic mentor, the Maggid, first appeared to him, he explained to Rabbi Caro what he should do to ensure the continuity of this revelation.
Know that I am the Mishna that speaks in your mouth. When you will be expert in the six order of the Mishna you will be elevated to the highest levels. The conduits of true wisdom will be open before you, for I am the Mishna and within me is true wisdom because I am the "mother" [bina, called "mother" in kabbala] about whom the verse states, "… the prophecy that his mother taught him" (Prov. 31:1). The Maggid discusses with Rabbi Caro the descent of the soul Therefore take care from today not to let your mind wander from the Mishna as you have done in the past, for although you occupy yourself with halachic decisions in which Rabbi Caro was a leading authority, which is a good thing, nevertheless, studying the Mishna will raise you to a higher level. So, "Grasp this, but do let go the other" (Eccl. 7:18), for together they are good. Take care that you do not fall into the category of those who forget even one thing of their studies,G‑d forbid.
(Maggid Meisharim, Bereishit)
The Descent of the Soul
Regarding the question you often ask, "Since the souls of the Patriarchs come from beneath the Throne of Glory, why was it necessary for them to descend to this [lowly] world? Now both answers that you usually give in response to this question are true. [What these answers are will soon become clear.]
For this reason, too, our Sages are divided over the issue of whether it would have been better for a person to be created or not. Now this [disagreement] is puzzling, since throughout each stage of creation the Torah states "and G‑d saw that it was good." Even regarding death, the Sages explain that the verse "and it was very good" (Gen. 1:31) alludes to death. If so, how could anyone even think of saying that it would have been better had man not been created? For this means that his creation is deficient, and G‑d forbid to say such a thing!
However, the secret of the matter is this: Until souls came to this world they were comparable to one who eats the king's bread without working for it. In that case it would be better had one not been created [even if only to reside in the supernal realms], for souls are ashamed to eat the king's bread without earning it. In order to avoid this shame, they wish to be created and to descend to this world and occupy themselves with Torah and mitzvahs "to work it and to keep it" (Gen. 2:15), and in this way they will eat bread without shame.
Furthermore, when [the souls] leave this world they rise up to higher levels than previous [to their descent into this world]. For [initially] they were hewn from underneath the Throne of Glory, and afterwards, [after living in this world], they rise up to be bound "in the bond of life with the Lord your G‑d"…Now when souls that did not rise up to the higher world [because they did not descend to this world] see the [subsequent] elevation of souls that were in this world, [they declare that] it is better to be created in order to merit the higher world.
The Maggid explains the secret of Eliyahu
[The other opinion] states that it would have been better for man had he not been created because the soul's entry into this world is fraught with danger. Perhaps they will do wrong and fall to a lower level [than previously]. Accordingly, it would have been better for them not to have been created and suffer the shame of undeserved bread.
Furthermore, it would have been better to remain cleaving to higher levels and "be bound up in the bond of life" (1 Sam. 25:29) and be satisfied with the level of "beneath the Throne of Glory" than to come to this world and enter into danger…
(Maggid Meisharim, Bereishit)
Seeing Eliyahu (Elijah) the Prophet
[The letters in Eliyahu's name, alef-lamed-yud-hei-vav, can be broken down into two parts, alef-lamed and yud-hei-vav. Thus] the name Eliyahu comprises chesed [as indicated by the Name E-l], and the ten supernal sefirot [indicated by] the Name yud-hei-vav -- yud signifies chochma; hei signifies bina; vav signifies the six sefirot from chesed to yesod, and implicitly includes malchut as ateret hayesod [and corresponding to them the letter hei, which is Matronita], malchut as an independent partzuf, [to become illuminated by all ten supernal sefirot]. Note that the three letters yud-hei-vav, together with the hei, form the Four-Letter Ineffable Name Yud-Hei-Vav-Hei, alluding to the fact that the Prophets spoke in the Ineffable Name of G‑d.
Now if you exchange the letters of the word navi, [nun-beit-yud-alef], using the Atbash formula, this renders tuf-shin-mem-tet. These letters, tash mat, come to tell us that the final hei [mentioned above], which is shemita [shin-mem-yud-tet-hei, the final year of the seven-year agricultural cycle, a word formed by combining the substituted letters, corresponding to malchut], is illuminated by the Jubilee, [the fiftieth year, corresponding to bina. The fiftieth year, the Jubilee, follows seven cycles of seven years and alludes to the perfection of the seven lower sefirot, similar to the festival of Shavuot, the fiftieth day after Passover, when we received the Torah - after the 49 days of counting the Omer].
With this secret of the final hei [of the Ineffable Name, which receives from the previous three letters, and] is therefore comparable to the body [that receives the soul], Eliyahu becomes clothed in a physical body and appears in this world.
Therefore, when you desire that Eliyahu appear to you, meditate on these matters when you go to sleep, and then he will appear to you…
(Maggid Meisharim, Bereishit)
When I am I
"If I am not for myself, who will be for me? And if I am for myself, what am I" (Avot 1:14).
If one does not accept the Yoke of Heaven, what holiness is there in emulating any of the Divine Attributes?
"If I am not for myself, who will be for me" means that if I do not grasp hold of the "I," namely malchut which is called ani, who will be for me -- that is, to which of the supernal sefirot can I dedicate myself?
Malchut represents the authority of G‑d, and dedicating oneself to malchut means accepting upon oneself the Yoke of Heaven. If one does not accept the Yoke of Heaven, what holiness is there in emulating any of the Divine Attributes?
"And if I am for myself, what am I" means when I grasp the "I," malchut, and I take it "for myself," for the lower malchut [malchut of the lowest world, Asiya, namely, the human individual, in this case "myself,"] as it says [in the verse], "Bone of my bone, flesh of my flesh," (Gen. 2:23) then "what [ma'h] am I?" This can be read as "I am ma'h," meaning that at that moment I join together the Name Yud-Hei-Vav-Hei [expanded to] the numerical value of ma'h  with ani, malchut. [In other words, when I take upon myself the Yoke of Heaven (malchut) and make it part of me, there is revealed upon me the Ineffable Name, whose transcendent, indefinable quality is alluded to in the word "what" -- ma'h]. (Maggid Meisharim, Ki Tissa)