Sometimes (often!) emotion can be mixed-- we hate what we love, we crave what will kill us, etc. I would suggest that we might want to generally stick to more pure emotion or all our characters will end up like Hamlet ("On the other hand...."), but at some especially intense moments, we might want to present the complexity of our characters' emotions. (This might be particularly dramatic in the Dark Moment, when the motivations, emotions, and conflicts collide.)
Here's a lovely example of mixed emotion:
I don't really have any wisdom, but perhaps you can find some good examples in your favorite emotion books of powerfully mixed emotion. All I can assess is that in these intense, complex moments, you might try juxtaposing the two emotions in the same sentence to show the conflict and overlap.
From that Poison and Wine song, and notice that the conjunction isn't "but" but "and"-- so the juxtaposition shows the conflict, but the "and" indicates the reality that both are existing in the same person and the same moment:
I don't love you, and I always will.
Syntax (sentence construction) is the perfect way to illustrate complexity-- everything in a sentence belongs together, so any contradiction will be heightened.
How about a short passage of mixed emotion done well? Here's one I like which shows the complexity of the adult child's resentment of the parents:
The contents of the boxes (plates and bowls, cutlery, serving dishes, pans and pots, a few extras that David insisted on, including a set of bowls for the children with famous sports figures on them—they’re sports fiends, the grandchildren) have been purchased so that Noelle, Amram, and their four boys can eat in their house. Noelle won’t eat off nonkosher dishes, even if those dishes belong to her parents. Especially, Marilyn sometimes thinks, if those dishes belong to her parents.
The World Without You by Joshua Henkin
The complexity is shown in the juxtaposition of those last two lines, and the opposition/pairing of "even if/especially if". The similar order of those two last elements highlight the changes (even if to especially if).
Other examples? What works to show the layering, the mixing, the conflict?