They may not believe your words; they may even laugh at you or cynically claim that you were just hoping to get on God's good side (so to speak), in case you didn't pull through.
But there is one thing they can't dismiss -- and that's the evidence of a changed life. Down inside, you know Christ has made a difference in your life; you know (for example) that He has forgiven you of all your sins, and that you have been saved and will go to be with Him in heaven forever. These are wonderful truths that should brighten your life every day. The Bible says, "This is the testimony: God has given us eternal life, and this life is in his Son. He who has the Son has life" (1 John 5:11-12).
But what difference has Christ made in the way you live? Do others see a joy and peace in your life that they didn't see before? Do they see you turning your back on things you know God doesn't want you to do, and showing love and compassion to others? God wants to make us more like Christ -- and He will, as we submit our lives to Him every day.
Pray for your friends, that God will convict them of their need of Him. And pray, too, that God will help you point them to Christ, not only by what you say but by the way you live.