Here's a headcanon(i think). Try thinking about the day Barry gave Lup before they became Liches, or vice versa
The day Barry planned out for Lup was simple. It started with a late breakfast together, both of them still wearing their pajamas from the night before, curled up together on a couch on the deck of the starblaster. They took their time to move to the next section of the day, Barry nervously and excitedly leading Lup through a dense forest near their ship. The walk took a good while, and both of them stopped throughout to excitedly look at a an alien flower, or prod blue tree bark. At one point Barry had sprawled out on his stomach to get a close view of some grass that seemed to move independently of the breeze when he caught sight of Lup, who was looking down at him with a wry smile. “You’re just cute when you get excited about grass babe.” He scrambled to his feet, blushing, and kept on moving, trying to stay focused.
They finally got to their destination– a gorgeous waterfall cascading into a clear blue pool. They spent the day swimming in the waters, splashing each other, laughing, maybe sneaking a kiss or two. And they spent the night drying off, talking to each other, reassuring each other of their love, and their strength.
As the day was ending, the two snuggled up together in bed, Lup turned to Barry and said through a yawn “Now I need to plan out your day, love. And you’ve really set the bar high here.”
Barry smiled, sleep in his eyes, “Every day I spend with you is the perfect day Lup.”