Yes, I completely agree. Instead of being upset with outcomes (like how people react to me in interactions), there's three things I've been trying to instead focus on: Am I at peace with my core values? Do my intentions align with those values? And finally, do my actions align with those intentions. If something bad has happened, and those three questions are a 'yes', then you have no reason to feel bad because you've been completely true to yourself and this occurence is something outside your control. If it's a 'no', then you probably need to do some reflection and figure out where in that chain something is going wrong.

If you say something unpleasant to a boss or someone else with the power to hurt you in life, even if it is aligned with your values (like enforcing boundaries or refusing unethical tasks), you may get fired, lose your income and destabilize your future safety, and have every reason to feel bad about your situation.

Still you might think, I did the best I could.

Epictetus would add that you need to act in accordance with "nature", by which he meant the world as it is, including human behaviour, not as we want it to be. In this case "nature" would include the behaviour of the boss and you can act accordingly, knowing that if you challenge them you may suffer repercussions.

I see your point but I’d argue that if you feel bad about this it means your core value is actually financial stability over sticking to your principles at any cost, and in that case your actions and intentions didn’t align with what you truly value.

Easy to say when you aren’t homeless or at risk of being made homeless.

For some folks, unfortunately, lying at times is a necessary survival mechanism.

I'm not disagreeing with you at all. If you value financial stability over taking a stand about things you might disagree with, then lying for survival is aligned with your values. Using the ideas I described above, this would be completely acceptable for the person doing that.