Their relationship is like this soft progression. The love Clara had for Eleven carries onto Twelve, and so does her expectations. Clara doesn’t expect him to return her affections, but in this iteration of the Doctor, he doesn’t think he deserves them. Twelve, he doesn’t do hugs at first because it’s a lie and he hates them in his self loathing way. But soon he needs them, needs to mask what his face might betray. Still, Clara catches on and when she dies, she thinks she knows how much he loves her and tells him not to say it, or it would make it impossible to say goodbye. But in the Cloisters, Clara comes to the horrible realization that the Doctor loves her so much more, so much more than his own life. She knows then that they have to say it this time. Say the words to each other before it’s too late.