If serving with the heart (Devarim 11:13) is called prayer (according to Ta'anit 2a), then what is the serving with the soul or serving with all one has in his ability mean?
The heart is considered the seat of the will. Rav Hisrch says on the pasuk
Thus, the conception of תפילה is given as "work on yourself" as being a penetration of one's whole being with enlightening thought ans ennobling feelings.
The soul in the first paragraph of the Shma is the emotions and desires while "might" is all one's physical resources (see Art Scroll siddur notes and the Mishna Brachos 9:5). This also includes martyrdom as we see in Rav Hirsch on Va'esachanan - Devarim 6:5
לבב is the heart of hearts, the innermost centre of the human organic body. נפשׁ: the living and striving personality מאד: the whole sum of means and forces, the "fortune".
As we have in the declaration of Independence; Our lives our fortune and our sacred honor
Rav Hirsch also says
בכל לבבך ... both the יצר טוב and the יצר הרע are to be used to serve Hashem
Yea, in truth, none of our inclinations are in themselves good or bad. All of them, the most sensuous of the sensuous ones, the most spiritual of the spiritual ones become good or bad according to whether or not they are usedwithin the limits, and for the purpose Hashem has allotted to each one of them, or misused, going beyond the limits, neglecting the purposes, or changing them for other purposes which Hashem has set for them.
Raav Hirsch continues regarding our existence
בכל נפשך ... not to think that this remaining in His proximity would be bought at too high a price by giving up the whole existence here below for it.
Rav Hirsch brings the story of Rabbi Akiva from Berachos 61b as an example of this concept.
Finally, we have the physical means of our survival.
ובכל מאודך: ... using all one's means in the service of Hashem as well as in renouncing every gain or acquisition which can only be obtained or kept through transgression of Hashem's laws.
... For מאד is not really only one's wealth of money but altogether the complex of all means for accomplishing anything and so comprises everything which the management of Hashem's Love measures out to us.
When the Chashmonaim refused to concede their avodat Hashem even in the face of mortal risk in a time of religious crisis (shaat ha-shemad- see Sanhedrin 74b; Rambam, Hilchot Chanukah 3:1, Hilchot Yesodei ha-Torah 5:3) they were applying the norms of kidush and ahavat Hashem. It is significant that the source and concept of ahavat Hashem- “ve-ahavta eit Hashem Elokecha be-kol levavechah u-bekol nafshecha u-bekol meodecha” - is the basis for the kidush Hashem of martyrdom (idolatry, and possibly shaat ha-shemad…see Sanhedrin 74b; Pesachim 25a; Rambam, Hilchot Yesodei ha-Torah 5:7), as well as the daily kidush Hashem obligation to represent avodat Hashem and halachic commitment constructively (Yoma 86a- “she-yehei shem shamayim mitahev al yadecha”; Rambam, Yesodei ha-Torah 5:11, though with a different source).