Each moral choice is different
Every time we have to make it difficult moral choice, there will be something new and different about it. So, applying the same rule every time is not going to work.
It doesn’t mean our values have changed. It’s more that the situations in which we apply them are different, and so we make different choices in practice.
This requires careful thought. Sometimes, we might find we’ve settled into ways of thinking that mean we’re applying rules, even if those are our own rules. We need to challenge ourselves, not just acting on what seems like instinct or intuition but going back to thinking carefully about consequences and virtues again.
Compassion is the basis of morality.