We all know that we cannot follow Jesus unless we follow him along the path of the cross. We have to die to ourselves, which dying includes denying ourselves those things which hinder us from joyful obedience and faith. When facing something that must be shed away from my life, it helps me to consider the fact that there is coming a day when I will be living without this thing anyway. This world, this age, is passing away. It will someday be gone. I, however, will be raised to live a new life in the world to come.
Now, faith realizes the future (Heb. 11:1). By faith I can imagine being utterly happy in another time (very weakly, of course, since, as Lewis reminds us, our desires are too weak). Why not go ahead and start celebrating? You will leave that sin behind someday anyway; go ahead and do it now. You will leave that pleasure behind someday anyway; go ahead and leave it now. You get the idea.
This is not contrary to the intent of our Creator for us to enjoy and be thankful for all the good he has given us in this world. This is not the same thing as practiced by those who want to leave off responsibility in this world and stand on a hill waiting to get "raptured." But, being sinners in this age (we will not be in the one to come), there is going to have to be a degree of self-denial. It's unavoidable. I find keeping the history of my life in the perspective of what has been revealed about my future, coupled with the eye of faith, to be a great motivation to enter now into the joy of the Lord by leaving particular things of this world behind.
What do you think?