Make it an element of the story, not the main focus. Adventure, suspense, mystery, or some other focus helps keep the story balanced. Focus on purity, privacy, and married intimacy rather than oozing emotion and sensuality between unmarried people. Fidelity, self-sacrifice, and playful fun help round out the romance. Keep it within the context of adults and near-adults and get them married as soon as possible or prevent the constant tug of physical temptation.
I have used the device of having the hero disabled in the second chapter and literally unable to move for most of the book. He is too busy wrestling with his self-pity, acknowledging his need to depend on others, and facing the danger of a second assassination attempt to worry about his romantic issues.
Another device I have used is to force the romantic characters into “arranged” marriage before they even acknowledge their love. The rest of the book describes their growth together in love, loyalty and dependence on each other, and some intimacy is expected.
A variation of the arranged marriage is one in which secrets and lies make love and trust impossible, keeping the characters apart until they can tell each other the truth and discover they are involved in solving the same mystery, at which point they can marry and work together to solve it.
Plenty of interaction with other characters and plot elements keep the focus off the attraction and strengthen the bond and commitment as the main characters go through the hardship or danger or mystery-solving together.