We're in Tehilim 33,21
כִּי־ב֭וֹ יִשְׂמַ֣ח לִבֵּ֑נוּ כִּ֤י בְשֵׁ֖ם קׇדְשׁ֣וֹ בָטָֽחְנוּ׃
In Him our heart is happy, Because in His holy name, we rely
This is a pasuk that we say in our Shabbat prayers, and for those of us that start from the beginning, it's found in Hodu every single day.
As we once mentioned, the Bet Yosef says, the rabbis put pesukim of bitachon into our prayers, and this is one of them. It discusses an important rule: “In Him, our heart will be happy because we relied on His holy name.” The sefer Shomer Emunim, in his essay on Bitachon, chapter 16, says that we see from this that it's impossible to find true happiness without bitachon.
Furthermore, the sefer Orchot Sadikim /Path of the Righteous (one of the more famous Mussar books) has different gates or topics. His Gate of Bitachon, which he largely quotes, almost verbatim, from the Hovot Halevavot, is placed in the middle of Shaar HaSimcha/the Gate of Happiness. He says this is because the only way to reach happiness is through bitachon. Based on this, the sefer Sror HaMor in Devarim 5,5 tells us that when a person says Keriat Shema, he must be in a tremendous state of happiness and remove all sadness and worry from his heart, because he is saying Hashem Echad. You have to be happy when you mention His name.
The Chafetz Chaim tells us that for any mitzvah that we do, especially Keriat Shema, we are standing in front of Hashem, involved in doing the work of God. Today, we don't have kings. But imagine a king or whatever celebrity would make you happy to be in his presence. And here we are, in front of God Almighty, Who can do anything! And, He's my Father taking care of me! How can I not be happy when I say Keriat Shema? I have to be full of simcha, ecstatic. That's the full simcha, that we're supposed to feel when we realize Who we're connecting to and Who we can rely on.
There's a story told in jest, of a rabbi that was asked by a certain man for the secret to success.
The Rabbi said, I'll leave two keys with you. And those keys will be the keys to success. The man heard of putting the key in the challah, but he couldn’t imagine what these special keys would be that the rabbi would leave with him.
He asked the rabbi where the keys were and the rabbi replied, “I was referring to the pasuk כִּי־ב֭וֹ יִשְׂמַ֣ח לִבֵּ֑נוּ כִּ֤י בְשֵׁ֖ם קׇדְשׁ֣וֹ בָטָֽחְנוּ׃
Key Bo Yismach Libenu, Key B’Shem Kodsho Batachnu/Because in Him, my heart is happy/Because in His holy name I rely. The “Key” to happiness is realizing that you're involved with Hashem. You're involved in His presence, and He's there for you to rely on. He wants you to rely on Him. That is the source of happiness. The Sefer Yesod V’Shoresh Avoda, Shar HaElyon,7th chapter, tells us that maybe when you're doing a mitzva, you might not be focusing on the simcha. But when you're saying this pasuk?!
Similarly, on Shabbat, we say, “Although we ate and drank, we did not forget Your Churban.” He says, you might not have thought of it in the middle of the meal, but while saying that line, at least then, have it in mind.
This is important. Find it in your prayers, and whether you say it every single day or only on Shabbat in Ranenu Sadikim, pay attention. It's almost like Keriat Shema. It says that if you say Keriat Shema without tefilin on, you're saying false testimony, because how can you say, “Put on Tefilin,” while not wearing tefilin? So too, you're saying the pasuk, “כִּי־ב֭וֹ יִשְׂמַ֣ח לִבֵּ֑נוּ
Because in Him, my heart is happy.” That's an emotional, real happiness, כִּ֤י בְשֵׁ֖ם קׇדְשׁ֣וֹ בָטָֽחְנוּ׃/
because I rely on His holy name. We have to think about these important concepts, of what it means to do a mitzvah, and what it means to say Hashem Echad, and that should fill us with happiness.