I've been thinking about an analogy that works to better understand what you mean by the "sample of His grace". Would it be something like the following?
God gifts us his initial grace. It would be like God giving us a very small plant in a pot, which we don't know what it will become. In accepting it, many of us rejoice greatly that God has chosen to give us something, especially from knowing our state of being a sinner. So there is a big wow factor for us. Now, going forward, we have to make two choices at least. Just like any gift, we can take care of it, or put it somewhere and forget it. In the second case, one can put the potted plant away, out of sight, and it will wither and die. We won't ever know what the plant really was.
In the first case, we take care of the plant and water it. As it grows, we plant it outside, and watch it grow into what it really becomes. Its a sort of work we still have to do, but truly, it would be a labor of love, and not hardship. One day, we see the plant has become a fruit tree. The branches are large, and it provides shade for us and others on a hot day. The fruits it produces brings a blessing to us and others as well.