Speech is easier than action
In the question: It is easier to assure or plan than to fulfill (the meaning varies).
("What shall we do with the word (Tehillim 33) and with the spirit in his mouth all their host? ... And the end of his knowledge is not revealed to us, for one may ask what is the taste of the word. And some say that the angels hear. And others say that they hear the sound of his word... And Rabbi Yehuda the Levite, may he rest in peace, said that the taste is without delay and without end and without time. And the word of the Torah is like the tongue of the sons of men, because the word It will be easier than the deed. And I have revealed to you the truth in detail" - Ibn Ezra, at the beginning of another chapter - Parush, chapter 1)
Translation
Expression (Hebrew)
הַדִּבּוּר קַל מֵהַמַּעֲשֶׂה
Definition (Hebrew)
בְּהַשְׁאָלָה: יוֹתֵר קַל לְהַבְטִיחַ אוֹ לְתַכְנֵן מֵאֲשֶׁר לְקַיֵּם (בַּמָּקוֹר הַמַּשְׁמָעוּת שׁוֹנָה).
("מָה נַעֲשֶׂה בְּמִלַּת (תְּהִלִּים לג) וּבְרוּחַ פִּיו כָּל צְבָאָם? ... וְלֹא גָּלָה לָנוּ סוֹף דַּעְתּוֹ, כִּי יֵשׁ לִשְׁאֹל מָה טַעַם לַדָּבוּר. וְיֵשׁ אוֹמְרִים שֶׁיִּשְׁמְעוּ הַמַּלְאָכִים. וַאֲחֵרִים אָמְרוּ לִשְׁמֹעַ בְּקוֹל דְּבָרוֹ... ור' יְהוּדָה הַלֵּוִי מְנוּחָתוֹ כָּבוֹד אָמַר כִּי הַטַּעַם בְּלֹא עִכּוּב וְלֹא כְּלִי וְלֹא זְמַן. וְדִבְּרָה תּוֹרָה כִּלְשׁוֹן בְּנֵי אָדָם כִּי הַדָּבוּר יוֹתֵר קַל מֵהַמַּעֲשֶׂה. וּכְבָר רָמַזְתִּי לְךָ הָאֱמֶת"- אִבְּן עֶזְרָא בְּרֵאשִׁית שִׁיטָה אַחֶרֶת - פֵּרוּשׁ פֶּרֶק א)