Obviously, you don't want to make your characters perfect or your story will be boring, so I wonder how you all balance out your characters flaws and the ways people in relationships will inevitably hurt each other without making it a really toxic red flag relationship.
I have a fairly easy time working that out with "Damsel in the Red Dress" because their romance is primarily based in friendship. They've spent a lot of time caring for each other physically or emotionally and still do, so though they do sometimes do things that hurt each other (like hiding things from each other, fussing at each other, refusing to admit feelings in some cases, etc.) it's pretty clearly balanced on the opposite ends by genuine, selfless love.
This is showcased the best in one of my favorite chapters "Black Bile."
And maybe I should be mad, or upset.
If today was any other day, I probably would have been crying ages ago, would still be paralyzed on the living room floor-
But all I see is the pain in his eyes, the beads of sweat making his long hair stick to his face and neck as he tries with everything in him not to cry - not to let me see him cry -
And if today was another day - if I felt better than I do now…maybe I would have thought of something comforting to say.
But today isn’t a day for making sense, apparently.
Don’t know what possesses me but I walk over to him without the slightest grain of hesitation - of bashfulness - of worry that I’ll regret this later and sit down on the edge of his bed, taking his face in both of my hands.
“Yah. Viejo.”
I can feel his furious heartbeat through the delicate skin - red and white and that perfect cashew brown all at the same time. I could find it in me to kiss him right now and forget about anything else - about reason and consequences - but instead, I press his forehead against mine and just breathe. I feel the heart skip beats, flip, somersault, and then calm down into a steady rhythm. I feel the skin growing hot under my fingertips, but I know if I open my eyes now, it’ll break the spell.
I whisper a sort of prayer my mother used to say to my brother and me when we were small.
Peace, my sweet, my heart.
“I can see you,” I say softly, “I’m no idiot, Kattar. We haven’t been friends for 15 years for me to be that blind.” The heart speeds into near panic -
Not this time - we’re not lying this time-
“You can pretend - pretend to be as angry and as cold as you like. I still see you. You don’t have to hide that you’re hurting from me.”
It's a little, though not a lot, trickier with "Hushabye Prince" because the mains weren't friends before their romance started, so their relationship starts based in attraction rather than actual love. However, I balance out their negative traits as well, because despite the fact that selfishness is a big problem for Jinwoo, he's also very sensitive to other's feelings. It seriously distresses him to see other people he cares about upset and he will try to do something about it, so if the thing/person distressing his loved one is himself, that means something needs to be done.
How do you work the balance out with your leads? It doesn't eve inherently have to be romantic partners, the same applies for siblings, friends, parent-child relationships etc.