It could be anything! The colors of sunrise in the sky, your kids getting out of bed, the smell of coffee brewing, a playful pet, a nice song, the sight of your partner in bed, the calmness of nature, the thought of a good friend, the challenges of the day ahead... this list is obviously not exhaustive.
Just describe, in as much detail as possible, what works for you!
I'm busy working on my blog posts. Watch this space!