There are two aspects to the action of God’s Grace:
One is “involuntary”. God sheds his Grace like the sun sheds its rays and its warmth upon everyone. The best example is being in the Most Holy Presence of Jesus in the Holy Eucharist. His Grace is constantly “filling the Temple, or Church building”, touching and blessing every one that approaches it, regardless of our response.
The other aspect is “voluntary.” It’s a simple act of the will… what we decide to do when God’s grace “knocks at the door of our heart” to come in, through His Church in the Sacraments, in His Word or in our fellow Christians. Or even in the different events of life… or in nature, when we come in contact with beauty, goodness and truth. A “golden chain” of daily “little yes’s” to God’s Grace in our “willing heart” could help us to become Saints some day.