Many, if not most of us, have done things in our lives that we deeply regret. We cannot erase the past, but we can allow the past to teach and guide us in the present.
Paul confessed that he had been a zealous and savage persecutor of the Church and was far from deserving mercy and grace from God. But that is the point. None of us 'deserves' or 'merits' grace and mercy - they are God's gifts.
God made Paul a great apostle and defender of the faith despite his past actions. His past led him to the present; it made him who he was. The same applies to us - our past can lead us in new directions.
In the narrative of Martha and Mary, we perhaps sympathise with Martha - after all, she was doing all the work! But the response of Jesus has two messages.
First, Mary has the right to be a disciple - as do all women - and to be taught by the Master. This is her birthright, and no one can take it away.
Second, it was a reminder to always focus on what is most important: God's presence and teachings. It is always too easy to be distracted and forget what is most important. God is most important - everything else is secondary.
Lord, keep me focussed on Your teachings.