Do Not Underestimate the Power of your Neshama
The possuk says (ז ז) וַיָּבֹא נֹחַ וגו' מִפְּנֵי מֵי הַמַּבּוּל and Noach came into the teivah, because of the water of the mabul. Rashi says that Noach only came into the teivah once the rains had started because he was מִקְּטַנֵּי אֲמָנָה הָיָה, מַאֲמִין וְאֵינוֹ מַאֲמִין because he was from those who had little Emunah. He both believed and didn't believe that the Mabul would come. Therefore, he waited to actually see the rain and only then entered the teivah.
The Kedushas Levi wonders what it means that Noach did not have complete Emunah. The Torah tells us (ו ט) נֹחַ אִישׁ צַדִּיק תָּמִים Noach was a complete tzaddik, as well as (ו כב) וַיַּעַשׂ נֹחַ כְּכֹל אֲשֶׁר צִוָּה אֹתוֹ ה' Noach did exactly as Hashem instructed him, which is also indicative of his complete Emunah. These two pesukim seem to contrast the former notion that Noach's emuna was lacking.
The Kedushas Levi answers that וְאֵינוֹ מַאֲמִין refers to the fact that Noach did not believe in his own koach as a tzaddik. He did not believe he was worthy of being saved more than anybody else. He thought that if a mabul would come, then surely he too would be destroyed, and therefore did not think it was necessary for him to enter the teivah.
For the same reason, he did not daven for his generation in the same way as other tzaddikim davened for their generation. He did not think his tefillos had any particular power. מַאֲמִין וְאֵינוֹ מַאֲמִין He did not believe in his own strength, he believed he was the same as everyone else, hence he did not capitalize on his greatness.
(קדושת לוי ד"ה אך נדקדק)