We make choices every day. Be it a right choice or wrong choice. They both have its own karma and we need to purify because they all have consequences.
I love the story about Buddha in one of his lifetimes as a Captain of a boat, if I recall correctly. And there were a few hundred people in the boat and one murderer/thief. Through Buddha's power of clairvoyance, he saw that the thief was going to kill everyone in the boat. So, in order to save the few hundred people, Buddha killed the thief himself. Though Buddha's act is noble and his intent is noble, Buddha still had to pay for the 'sin of killing'. For that, I think it was said that Buddha spent a day in the Hell Realm.
Now, Buddha had a lot of merits and spiritual attainments to support him. Whereas we do not.
Most fo the time, we can't even truly tell if our own motivations are pure or even right.
So, we must always purify and pay for everything that we have done wrongly every single day.
It would help a great deal when we do not add to that list of wrongly deeds anymore too.
Hence, Dharma is a living practice.
We practice every day, every moment, with every thought and with every breath we take. And we do our best to do the very best we can, with what we understand. As long as we keep learning, we will gain real knowledge and higher understanding. This allow us to see more and do more good - not just for ourselves but also others.