He is not so splendid as you described him/ the "lion" you mentioned is but a "fox"
In the question: The brave one will become fearful. He will lose the courage he had (Ary means lion).
("Rabbi Yochanan said to R. Sh. Ben Lakish: "What you said will become a fox!" - Baba Kama Kis 17a)
Translation
Expression (Hebrew)
הָארִי נַעֲשָׂה שׁוּעָל, אֲרִי שֶׁאָמַרְתָּ נַעֲשָׂה שׁוּעָל
Definition (Hebrew)
בְּהַשְׁאָלָה: הָאַמִּיץ נִהְיֶה פַּחְדָן. אִבֵּד אֶת הָאֹמֶץ שֶׁהָיָה לוֹ (אֲרִי מַשְׁמָע אַרְיֵה).
("אָמַר לוֹ רַבִּי יוֹחָנָן לר"ש בֶּן לָקִישׁ: אֲרִי שֶׁאָמַרְתָּ נַעֲשָׂה שׁוּעָל! "-בָּבָא קַמָּא קיז ע"א)