Justification seems to be related to specific human acts revolving around what we do, say and think. For instance, anything we do, if we do it in righteousness—or often even with a righteous desire which falls short of righteousness (through God’s tender mercies and loving kindness)—may be justified by the Holy Ghost. This may be any brief and finite action we take, such as giving a talk at Church, bearing a testimony, forgiving someone who has hurt us, speaking a word in kindness, feeding the poor, or showing mercy.
We often feel the strong presence of the Spirit at those times, confirming that our offering before the Lord has been accepted. For instance, if we share a testimony humbly and teach by the Spirit “the Holy Ghost shall be shed forth in bearing record unto all things whatsoever ye shall say” (D&C 100:8b). I believe that usually we will also receive a confirmation by that same Spirit, “Wherefore, he that preacheth and he that receiveth, understand one another, and both are edified and rejoice together” (D&C 50:22). Longer efforts may, in the same way, be justified or be accepted by the Lord, such as serving a mission, magnifying a Church calling, being faithful in our employment, or having a temple sealing ratified by the Holy Spirit of Promise. Of course, we are not aware of all the positive effects of our actions in this life. To summarize, then, it is what we do together with the eternal effects of the atonement of Christ—wherein the imperfection in our offering is coupled with the perfection in His Holy offering—that brings about justification, or the acceptance of this offering we brought to the Lord.
While justification has to do with a stamp of approval—or the acceptance of our offering before the Lord—sanctification appears to be the long process wherein we are transformed into a different, holier being. Wherein we begin to become like the person we hope to someday be. Like justification, we can never do this on our own merits. Rather, it is through the grace of Christ as the result of His holy expiatory sacrifice, after we “have expended [our] own best efforts” (Grace, LDS Bible Dictionary), that we are slowly changed or sanctified that we may in time enter into the presence of the Father. Satan attempts to discourage our efforts by pointing out our weaknesses. Yet the Holy One of Israel is continually inviting us to turn unto Him, put our trust in Him and become His disciples. As with justification, we also have manifestations of the spirit—such as a great joy and feelings of gratitude—that help us understand that indeed this transformation is beginning to take place.