When it comes to how to make characters’ emotions feel real, the best advice I’v been able to dredge up is that you must feel it yourself. The moments when my descriptions of characters’ emotions come out the best is when I’m immersed in their emotional state.
I once wrote a scene in which a character cried—I can’t remember why he was crying, but honestly I put him through the wringer for that whole novel, so there could have been any number of reasons. It was one of those days when the words start flowing and don’t stop for a good hour, and when I came out of it, I felt like I had been crying myself. I had all the symptoms—the kind of drained feeling, the tight face, the wobbliness of a good cry. But I most assuredly had not been actually crying—only writing, immersed, about a person breaking down.
But sometimes (often) I read over my descriptions and the emotions are stiff and clunky, completely unconvincing. I’ll revert to simply telling instead of showing, never a good idea. But the best case scenario is when you’re right there with your character, feeling their pain and joy and embarrassment (that’s possibly the worst one, let’s be honest).
There’s no magic formula to get you into that space. Sometimes you have to leave a gap in red text that says “insert emotional moment here”. Sometimes you make yourself write something crappy, break out the ‘she said sadly’s and the ‘he felt happy’s and go back and fix them later. But one way or another, that emotion has to make its way onto the page. It has to be strong enough to make not just the writer feel it, but the reader too.