A person can know that Hashem gave us the Torah and still commit many sins. This is because emunah that functions only on an intellectual level is incomplete. Though it certainly is beneficial, it lacks the life-changing benefits that come when we feel emunah.
Intellectual knowledge has only a minimal impact on our decisions. If we do not feel emunah, then when we are challenged we will find ourselves subtly feeling that our actions lack consequences. Intellectual emunah also isn’t enough for us to live with the palpable feeling that Hashem is present. Therefore, our job is to take our intellectual knowledge and make it real until it permeates our essence.
Even when we reflect on the evidence and are confident that Hashem gave us the Torah, the feeling will not last long unless we review the evidence frequently. Emotions lose their potency over time, and our ability to feel this truth will slowly fade unless we constantly fortify it. Even those who witnessed Hashem’s revelation at Har Sinai were commanded to review it, relive it, and invest special effort not to forget it (Devarim 4:9-10; see Ramban there). Thus, once we have internalized that Hashem gave us the Torah, we must constantly strengthen this feeling so it does not lose its potency.
One way to boost our ability to feel Hashem’s presence is to read a section of a book about emunah every night. Over time, this will bring us to constantly remember that Hashem is with us, and we will even be able to feel His presence. This will also help us maintain these feelings so they don’t slip away.
It also is beneficial to frequently think about the kindness Hashem does for us daily and to read about His kindness to our nation. We need to remind ourselves at all times that Hashem loves us and only does good for us. This is crucial for cultivating a relationship with Hashem and feeling that He is present.