Our Gemara on Amud Aleph relates a Midrashic retelling of a Biblical story. The Torah (Shemos 15:22-25) states:

וַיַּסַּ֨ע מֹשֶׁ֤ה אֶת־יִשְׂרָאֵל֙ מִיַּם־ס֔וּף וַיֵּצְא֖וּ אֶל־מִדְבַּר־שׁ֑וּר וַיֵּלְכ֧וּ שְׁלֹֽשֶׁת־יָמִ֛ים בַּמִּדְבָּ֖ר וְלֹא־מָ֥צְאוּ מָֽיִם׃ 

Then Moses caused Israel to set out from the Sea of Reeds. They went on into the wilderness of Shur; they traveled three days in the wilderness and found no water. 

וַיָּבֹ֣אוּ מָרָ֔תָה וְלֹ֣א יָֽכְל֗וּ לִשְׁתֹּ֥ת מַ֙יִם֙ מִמָּרָ֔ה כִּ֥י מָרִ֖ים הֵ֑ם עַל־כֵּ֥ן קָרָֽא־שְׁמָ֖הּ מָרָֽה׃ 

They came to Marah, but they could not drink the water of Marah because it was bitter; that is why it was named Marah. 

וַיִּלֹּ֧נוּ הָעָ֛ם עַל־מֹשֶׁ֥ה לֵּאמֹ֖ר מַה־נִּשְׁתֶּֽה׃ 

And the people grumbled against Moses, saying, “What shall we drink?” 

וַיִּצְעַ֣ק אֶל הי וַיּוֹרֵ֤הוּ ה׳ עֵ֔ץ וַיַּשְׁלֵךְ֙ אֶל־הַמַּ֔יִם וַֽיִּמְתְּק֖וּ הַמָּ֑יִם שָׁ֣ם שָׂ֥ם ל֛וֹ חֹ֥ק וּמִשְׁפָּ֖ט וְשָׁ֥ם נִסָּֽהוּ׃ 

So he cried out to Hashem and Hashem showed him a piece of wood; he threw it into the water and the water became sweet. There [God] made for them a fixed rule; there they were put to the test.

Our Gemara says it was not really water for which they thirsted, but actually Torah. This is why the rabbis established that there should be a public Torah reading every Monday and Thursday. Counting the reading on Shabbos, there never would be a period longer than three days without Torah.

Peri Tzaddik (Rosh Hashanah 5) develops this idea further in a fascinating essay. When the Jews were in Egypt, their souls were constricted and unable to comprehend and appreciate the beauty of the Torah. The Hebrew word for Mitzrayim shares the same root as the Hebrew word tzar, which means narrow. The Egyptian impurity of the soul created a constricting narrowing effect. Zohar (III:151) reads this same idea into the verse (Shemos 1:14):

וַיְמָרְר֨וּ אֶת־חַיֵּיהֶ֜ם בַּעֲבֹדָ֣ה קָשָׁ֗ה 

Ruthlessly they made life bitter for them with harsh labor 

Zohar interprets “Life” as Torah, because of course to a Jew, Torah is life. The Egyptians with their constriction and oppression, took the life out of their Torah.

When the Jews were finally rescued and experienced the miraculous events at the Red Sea, the Midrash teaches us that they were catapulted to a high level of prophetic insight. “A maid-servant beheld at the Red Sea what even the prophets never saw (Mekhilta d'Rabbi Yishmael 15:2:2).” However, since this was not a state that they attained through hard work, they lost it immediately after leaving the Red Sea. Even though earlier, they found the Torah and encountering God’s will as pleasant, it reverted back to being bitter again. That was the bitter water that they encountered in verse 23. However, Moshe was able to guide them and teach them to recover their spiritual sensitivities, to the point that they could appreciate the Torah and no longer find it better.

Hoshea (14:10) states:

מִ֤י חָכָם֙ וְיָ֣בֵֽן אֵ֔לֶּה נָב֖וֹן וְיֵדָעֵ֑ם כִּֽי־יְשָׁרִ֞ים דַּרְכֵ֣י ה׳ וְצַדִּקִים֙ יֵ֣לְכוּ בָ֔ם וּפֹשְׁעִ֖ים יִכָּ֥שְׁלוּ בָֽם׃ 

The wise will consider these words, The prudent will take note of them. For the paths of GOD are smooth; The righteous can walk on them, while sinners stumble on them.

This underlines an important quality of Torah. When you are healthfully immersed in the system, Torah is experienced as sweet and life-giving. However, if something happens and you become alienated and feel like an outsider, what is sweet in the Torah starts to feel bitter. The path back can feel difficult and elusive for some.