Ask Me, and I shall give you nations for your inheritance, and the uttermost parts of the earth for your possession.
Rashi explains the words שְׁאַל מִמֶּנִּי, to daven to Hashem at any time of battle with an enemy. התפלל אלי בכל עת שאתה בא להלחם באויביך
The שְׁאַל מִמֶּנִּי type of prayer is available to us specifically during war and when we do this it comes with the promise of our Nachalah and Achuza as described in the verse during war with our enemies. (If we look at the pasuk the words שְׁאַל מִמֶּנִּי comes with the granting of וְאֶתְּנָה גוֹיִם נַחֲלָתֶךָ וַאֲחֻזָּתְךָ אַפְסֵי־אָרֶץ).
The connection of שְׁאַל מִמֶּנִּי to the granting of our inheritance; dominion over the nations, and our lands from Hashem Himself (not limited, or cut up, or with conditions) is telling us something about this prayer.
Then, if we look at the previous verse in Tehillim , it states: בְּנִי אַתָּה אֲנִי הַיּוֹם יְלִדְתִּיךָ, My son, you are before me, as I today have given birth to you.
The word Today, Hayom is alluding to Rosh Hashana according to Rashi. Rosh Hashana is Yom Hadin.
And Hashem is relating to us as His Child.
This tefillah is one that activates a specific response of inheritance and possession.
It contains Hayom; related to Rosh Hashana
It relates to us as a newborn Child
Therefore, to me it seems as if we have the ability at any time of war to access this influence of Rosh Hashasha. If we daven in a way of שְׁאַל מִמֶּנִּי, we then activate the promise of our Nachala and Achuza.
On Rosh Hashana we are focused on Hashem being our Parent Who is Melech; our only source of life. It seems to me that when need to go to Hashem as a newborn baby when we cry out to Him. Without all the baggage that came afterwards.
The Daas Zekeinim furthers this point as he explains that the word שְׁאַל, means a request to be given as a gift. He explains that the same word is used when B’nei Yisroel requested trinkets from the Egyptians. The Egyptians did not expect payment or for them to be returned; it was a gift.  B’nei Yisrael accessed this when they were on the 49th level of impurity. The gifts were not conditioned on their worthiness.
The mechanism of שְׁאַל מִמֶּנִּי, is not conditioned on our worthiness, but the worthiness is the act of prayer as a שְׁאַל מִמֶּנִּי.
This prayer of שְׁאַל מִמֶּנִּי is available on a time of Din; every time we go to battle.
Because we are told the outcome of this prayer of שְׁאַל מִמֶּנִּי, I imagine our prayers need to be directed with this outcome in mind; our full inheritance, and land as promised.
Don’t ask others; other nations permission from what is Mine! Ask for all from ME and only ME, as a newborn to his father/ mother without any barriers.
May we all join in the original Tefillah of Hashem ,and ask Him for gifts right now, for Him to present us with the eternal gifts He prepared for Klal Yisrael at the moment of creation; וְאֶתְּנָה גוֹיִם נַחֲלָתֶךָ וַאֲחֻזָּתְךָ אַפְסֵי־אָרֶץ, I shall give you nations for your inheritance, and the uttermost parts of the earth for your possession.