11 For the grace of God that bringeth salvation hath appeared to all men, 12 Teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly, in this present world; 13 Looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ;
A godly life must rest on the twin pillars of "grace" and "the blessed hope."
John tells us in his epistle that if we have the hope of the rapture before our hearts, which is what is referred to by "the blessed hope," that we purify ourselves, even as He is pure. The assurance of His imminent return has a purifying effect in our lives, for we would want to be found living righteously when He comes for us. If we lose sight of His returning for His saints, an event called the rapture and here, the "blessed hope," then one of the pillars crumbles and we become weary along the way, burdened with living a holy life instead of enjoying it in the power of God. As 1 Cor. 15 puts it, "we are of all men, most miserable."
Verse 11 mentions that we become aware of the need to live godly and righteously, denying the temptations of the world's attractions and sins through grace. Grace is what teaches us that and then enables us to live it(see also Rom. 7:24 - 8:4 and Eph. 2:5-10). If we are depending upon our own will power to live godly in this world, then one of the pillars crumbles, and our life ceases to be godly.
May these twin pillars stand straight, firm, and tall in our lives.
"'Twas grace that taught my heart to fear,
And grace my fears relieved;
How precious did that grace appear
The hour I first believed!"
from "Amazing Grace"