I stare deep into my crystal ball, allowing it to reflect myself, to encompass everything of who I am. Through my reflection on its surface, I gaze into its misty, murky depths, hoping to catch a glimpse of my essence, my self.
For long hours, I ponder. For long days, I stare. Eventually, in the depths of the reflection, I see a dim shadow, spiraling. What is this secret? What aspect of my soul has struggled into view?
As the shadow takes form and clambers into being, I see that is not an image but a symbol. An E? An ε? No, it is a 3.
Mystified, unsure, I study my crystal ball further, pouring more hours, more days into the endeavor. Surely there is more I can glean, more self-knowledge I can attain. With great effort and determination, another tenebrous form swims into view. Another secret to behold.
It swirls and resolves and becomes real. Another symbol. An L? A Λ? No, a 7.
I stare and I ponder, I ponder and I stare, but my crystal ball shows me naught but milky white. Its depths have nothing more to give. It reflects no more of my self.
Why did my crystal ball show me a 3 and a 7, and nothing else?
To clarify: The only possible numbers the crystal ball could have shown me are 3 and 7. I could not have posted this puzzle with any other numbers in the place of 3 and 7.
While @Amoz has given a lovely answer, I also want to nudge people towards discovering the answer I intended. Towards that end, I will give a hint.
If you point at my name, you will see an important number.