Adapted from The Council of Orange (529 AD)
I would almost say that the problem of grace is more of a problem to those within Christianity than the problem of evil. The very act of God that enables our belief, assures our sanctification, and commands our obedience is also the very thing that is so hard to stomach. This is largely because of pride, combined with a distortion of the image of God in us. We want to assume that our agency enables us to follow the commands of God, and thereby lay hold of our salvation through our own merits. This often leads to a checklist-and-penance mentality: the more good things we do for God, the better off we are with him and if we're not doing things right now. . .it'll be okay because we're going to do even better things to make up for what we're not doing. The problem is with action, and who exactly is acting.
Action is a sticky subject, and hard to break down because it looks different in the Christian life. It is my firm belief that the doctrine of grace does not permit inaction on the part of the believer, but enables the believer to act. This action, however, in its strictest sense, does not come naturally from the person himself, but only from Christ, who being the "Author and perfecter of our faith" (Heb 12:2) assures that we will be like him (1 John 3:2; Romans 6:5). It is God, not man, who is always working (John 5:17). Through our union with Christ, we partake in the divine work, without ultimately doing anything. Grace leads us to our work: reconciliation (2 Corinthians 5:18), and loving one another (John 13:34-35, 1 John 4:11-12). This is as great of an apologetic as has ever been conceived.
Accepting this grace is the start. It is sufficient to work in our weaknesses (2 Corinthians 12:9) and help us bear our afflictions. It enables us to enter into the place of rest (Heb 4) and gives us assurance that his yoke is light (Matthew 11:30), and his burden easy.