Christ paid the price for our Salvation.  When he said "It is finished", it was Paid In Full.

If we walk away from the cross with only this in mind, we are missing the importance of what happened AFTER the cross.  For three days Jesus did things that would eventually set up his Kingdom on Earth.  

If we, the Church, just go to church, sit and listen to a sermon, and don't do another thing to further the Kingdom until the next "visit" to church, we are missing the mark.  Jesus took things out of the grip of Satan and placed them into our hands.  

If I do not use what gifts Jesus gave me, gave us, he will give them to someone who is a willing vessel ready to use those gifts for His Glory.