Summary: Everything a believer does is aimed at impacting others for Christ...or should be.
Therefore, my friends, since we have confidence to enter the sanctuary by the blood of Jesus, by the new and living way that he opened for us through the curtain (that is, through his flesh), and since we have a great priest over the house of God, let us approach with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. Let us hold fast to the confession of our hope without wavering, for he who has promised is faithful. And let us consider how to provoke one another to love and good deeds, not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day approaching.
Hebrews 10: 19-25 (NRSVA)
Some time ago I got an email from a friend who sent me a whole sheet of those “letters to God by children”; one of them was:
Dear GOD, It rained for our whole vacation and is my father mad! He said some things about You that people are not supposed to say, but I hope You will not hurt him anyway. Your friend (But I am not going to tell you who I am).
There is a phrase in our text that evokes a picture. That phrase is “through the curtain”. The sky was clear the morning they led Jesus through the streets of Jerusalem to Golgotha. The sky didn’t stay clear! Near mid-day the sky went dark; three hours later it was still dark when Jesus breathed his last agonizing words: “it is finished”.
At that moment the earth began to shake like a bad California day. Matthew tells us the earthquake was so violent huge rocks were split in two. Tombs were opened when this happened; corpses were raised and they were seen walking in the cities nearby.
Notice what else happened:
At that moment the curtain of the temple was torn in two, from top to bottom. Matthew 27:51a (NRSVA)
This is the curtain Paul mentioned when he wrote to the Hebrews of how Jesus made a way for us to enter God’s presence. The curtain was a separation in the Old Testament temple. It separated everyone from the holy presence of God. The reason for the veil was sin. The very reason that veil separated the place where God would show up from the place where man stood is the difference between a holy God and sinful men. The veil represented the darkness of having no hope to approach God.
Sin is that which takes our hope away and makes life unbearable. Author Lee Stroebel talks about hoping for success in explaining Easter. He tells how his brother-in-law tried to do that with his 5-year-old son Sean. “They were sitting in church on Easter, and just before the service began, my brother-in-law pointed to the cross and said, ‘See the cross? The people put Jesus on the cross. The people killed Jesus.’ Sean looked around very nervously, then asked cautiously: ‘These people?’" 
That is always the reaction; we are astonished that we have the capability to put God to death – yet the very presence of the curtain said so!
When that curtain was torn in two it was because the sacrifice of blood on the cross was final; it was a victory over sin and death.