It's like a free gift that wrapped up and left for you on your table. It is yours in the sense that it belongs to you, but unless you unwrap it there is still a sense that you have not fully received it. Or receiving a DVD as a free gift that is still in its packaging on your shelf, where the gift was not a paper weight, but to watch a movie. Or receiving a lifetime of college tuition as a free gift, but you still need to attend classes to fully receive it. According to Titus 2:11-14, our salvation involves being trained by grace to do what is godly, righteous, and good and to renounce doing what is ungodly and sinful, so the free gift of salvation involves ongoing training that we are receiving by grace.