I HATE unfinished business with another, don't you?? Mine sits upon the back-burner of my stove on a low simmer, until I clear it off. This robs me of energy (however slight or subtle) that I'd rather devote to pursuits more productive.
When someone who's crossed ya presents you with a chance to express what ya never had opportunity to before, it can feel very freeing. You get to move that old crud that's been sitting around in your system, OUT of your body.
You might second-guess yourself, especially if your words are tinged with anger, but it's still healthier for you to get that shit up and out of you, than to let it linger and fester.
Contrary to popular belief, not one of us can get thru an entire lifetime without disappointing or hurting another. Nobody's capable of always living up to the expectations of others, without throwing themselves under a speeding bus.
The sense of confinement and 'stuck energy' in our body if we DON'T express our truth, can eat away at our insides like a cancerous growth. I do NOT recommend censoring yourself for THIS reason, alone!
Each of us has a dark side. Most try to amputate this aspect out of their personality repertoire, and dance ONLY in the light~ for to do otherwise, means (to them) they're a "bad person." I say, horseshit to this!
If you cannot accept and embrace ALL the parts of the Self that are You, you are not capable of being a whole and healthy individual. I'm not suggesting you go thru life disregarding the feelings and needs of others~ I'm merely encouraging you to let yourself be HUMAN, replete with all the emotional facets you were born with, and meant to retain and embrace.
If you one day allow your darkness to convey the unspoken, locked up emotions you've been sitting on for perhaps years, you've done a GOOD thing for your own well-being AND given the other a chance to reflect on what might still need developing or healing within themselves!
Bottom line, if you never say "OUCH!" when someone steps on your toes (be it unwitting or not), they blithely continue on their life journey without A CLUE about what in them needs changing, in order to elevate themselves to the next rung of their soul's evolution . . .
and we're all interested in EVOLVING into our ever-improving Self, aren't we??