Have you 'mastered' salvation by grace?

I've been recently lamenting the fact that I so struggle with legalism - that I struggle to really get the gospel of grace. Martin Luther is one of the most helpful theologians for this type of feeling.

Martin Luther:

“Particularly when you hear hear an immature and unripe saint trumpet that he knows very well that we must be saved by the grace of God, without our own works, and then pretend that this is a snap for him, well, then have no doubt that he has no idea of what he is talking about and probably will never find out. For this is not an art that can be completely learned or of which anyone could boast that he is a master. It is an art that will always have us as pupils while it remains the master. And all those who do understand and practice it do not boast that they can do everything. On the contrary, they sense it like a wonderful taste or odor that they greatly desire and pursue; and they are amazed that they cannot grasp it or comprehend it as they would like. They hunger, thirst, and yearn for it more and more; and they never tire of hearing about or dealing with it, just as St. Paul himself confessed that he has not yet obtained it (Phil. 3:12). And in Matt. 5:6 Christ calls those blessed who hunger and thirst after righteousness.”