Looking at post-Christian Europe, and nearly post-Christian America, it is alarmingly evident how rapidly the Gospel can lost. Mack Stiles, in his book Marks of the Messenger points out the decline.
Generation 1: The Gospel is Accepted
Generation 2: The Gospel is Assumed
Generation 3: The Gospel is Confused
Generation 4: The Gospel is Lost
(Stiles, pg. 40)
NEVER assume the Gospel. Preach the Gospel. If the Gospel is to you nothing more than a means of avoiding Hell, you've already confused it! The Gospel is for all of life.
Don't assume the Gospel. If you are confused, get clear on the Gospel. And, if you are in a church that has lost the Gospel, do all you can to bring it back.
1 Corinthians 15:1-4 (NIV)
Now, brothers, I want to remind you of the gospel I preached to you, which you received and on which you have taken your stand. By this gospel you are saved, if you hold firmly to the word I preached to you. Otherwise, you have believed in vain.
For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures, that he was buried, that he was raised on the third day according to the Scriptures.