When it comes to evangelism, much is said about God's love, God's mercy and God's grace. There is a lot said about how he loves us and forgives us, but very little is mentioned about the Law of God, the judgement of God, and the consequences for violating his law.
The word Gospel means "good news", but the reason it is good news is because of the bad news that the law reveals. This contrast between the bad news is why it is such good news.
The bad news is that we all have broken God's law. Have you ever lied? stolen? looked with lust? used God's name as a curse word? hated someone? who can say they have never sinned?
"For all have sinned and fall short of the glory of God" Romans 3:23 ESV
We are all violators of that law. Therefore we come under guilt and condemnation and with condemnation comes punishment, and that punishment is everlasting.
"For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord." Romans 6:23 ESV
The gospel cannot be understood as good news, until we understand what it delivers us from, namely the bad news of eternal punishment.
When we witness to someone we often try to get them to Heaven without letting them know that they are on their way to Hell. We are trying to get them to accept what is good for them without them understanding the truth about what is so bad for them.
"What does Jesus save you from?"
We shouldn't be reluctant to to talk about the Law of God, because it makes people feel bad. When in fact, it is necessary to make them feel bad, really bad, because that generates the true attraction to the gospel.
Jesus said "They that are whole have no need of the physician, but they that are sick: I came not to call the righteous, but sinners to repentance." Mark 2:17 KJV
Spurgeon said it this way "Who can say the law is too severe when the lawgiver himself submits to its penalties."
Telling you what you have done wrong first actually enables the good news to make sense. The Bible says "For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God." 1 Corinthians 1:18 KJV
If I don't clearly show you that you have broken the law, then the good news will seem foolish and offensive. But once you have understood that you have broken the law, then that good news will become good news indeed.