Before you explain how you feel to someone else, explain it to yourself in one sentence.

Confusion in your head is not mysterious, it is unfinished. A feeling you can only gesture at comes out as a long tangle, and whoever is listening has to reconstruct it while also reacting to it. Getting it into one sentence first forces you to decide what the actual request or complaint is.

Write the one-liner before the hard conversation, on paper or in your notes. If you cannot get it under a sentence, you are probably carrying two separate things and should say them separately. Then lead with that line instead of the backstory.