Adopting an attitude of universal responsibility is essentially a personal matter. The real test of compassion is not what we say in abstract discussions but how we conduct ourselves in daily life.
-His Holiness the Dalai Lama, "Imagine All the People"
Just talking about harmlessness isn't enough.
When spiritual practice (meditation) does not lead to reciprical compassion from others, a person's conduct should still be to practise harmlessness.
To feel guilty for past wrongs is not enough - one must strive to learn from one's mistakes.
Even in the Dhammapada it is written to not cling to regrets and worries.
Dhammapada 67-68:
It's not good,
the doing of the deed
that, once it's done,
you regret,
whose result you reap crying,
your face in tears.
It's good,
the doing of the deed
that, once it's done,
you don't regret,
whose result you reap gratified,
happy at heart.
As well, the cure for regrets about wrongs done is simply letting go:
348:
Gone to the beyond of becoming,
you let go of in front,
let go of behind,
let go of between.
With a heart everywhere let-go,
you don't come again to birth
& aging.
Thus what the Dalai Lama says about the real test of compassion is ... how we conduct ourselves in daily life.