I think we all hold that "secret" within us, Juin.
Some of us hold a child-like curiosity & interest as to what every day may hold for us, what joy or new knowledge or new experience it may bring? My grandfather was exactly like that, and he was a strong influence on me.
My grandfather never lost that childlike enthusiasm for the secrets and experiences every new day may hold & reveal. Every day for him was a new place to go or see, or a new activity to try. And during his retirement when I was not in school, he took me with him wherever his adventures called. In fact, it was this same need for adventure that brought him to America at the age of sixteen, starting our family in the New World, a place filled with new things & new possibilities waiting to be discovered.
His infectious personality rubbed-off on me.
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But also,
In the external sense, I also believe the secret is to surround yourself with people you love and who love you.
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A confirming example of why I can say all the above so adamantly & confidently, actually just occurred over the weekend. In total happenstance serendipity, by a lucky random chance crossing of paths & events, a person from my childhood came back into my life - and was overjoyed to see me.
Despite my strong childhood feelings towards this person, I thought they had spurned me way back then. They had simply disappeared. Never to be heard from again. It turns-out we became separated due to their family events beyond their control. But they had always had the same strong feelings & longing I did. But, without any contact between us I never knew this.
The mutual loss of our childhood relationship was an unresolved conflict for me, even as I grew over it and it receded into the shadows of my mind & soul. But this weekend it came back to the forefront, and was joyously resolved! We spent the entire evening wrapped in discussion, proclaiming the tragically cut-off mutual childhood joy we had for each other, the current joy we we now had for finding each-other again, and the wonderment of the chance coming back together after a long lifetime of separated years! Our story of separation and reuniting could make a published short-story!
I am still riding a high over our reunification, and knowing that we will now remain part of each-others' lives going forward!
And that, Juin, is why I greet every day excitedly for the wonderment it may hold for me!
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tl;dr hold childlike wonderment at the opportunity for the discoveries and unexpected joys each day may reveal, and surround yourself with those you love and love you