You just have to write it.
And then write it again.
And you keep writing until you’ve used your imagination, the creative drive that’s pushed you to write your story with your characters, to get your characters where you want them to be. And then when you’re looking back over everything you’ve written (because you should always save multiple drafts) you decide if there’s anything salvageable from Draft 87b—and in working that in with your current draft, you find that there are elements, phrases, sentences, from Drafts 13 and 59C that work perfectly in bridging Draft 87b in with your current draft. And then you get a new current draft and the old current draft becomes Draft 142.
If you’re using your imagination and your influences in your writing, that’s perfect! That’s what you’re supposed to do. Mixing all that in with your life experiences is the fundamental keystone to writing: it’s the definition of storytelling. If you’re feeling burnt out and exhausted, take a break. Go read your favourite book, watch your favourite movie or your favourite season of your favourite TV show. Go for a walk downtown, to the beach, the park, forest. Take a job or exercise in your preferred way to get your body working, blood flowing. Take a long bath with a scented candle and a generous helping of bath salts and oils. Sometimes unwinding from your world is the only way of clearing your head when you’ve been stuck for so long on how to make Plot A move into Plot B, and that applies to romance, tragedy, thriller, and everything. Once you’ve completely relaxed and eased all the narrative tension from your synapses you can come back to your work and examine Draft 142—and then after that’s done with, you’ll have Draft 142b.
But the first step before all that is to just write it. And keep writing it. Give up on getting it perfect and write it—write the crap that you know it will be because you’re unsure of how to form this relationship, the commentary on romance and love you want to make, and the way your characters bruise their hearts on each other. Forget about perfection and just write it. That’s the only way to strengthen your imagination and your ability to put down your imagination in words.