I know this is a hard reality to understand. This makes my heart hurt every time I think about it. The thought of people I love not spending eternity in heaven pierces my very depths. For this is the reason I feel compelled to share this and faith as a whole. I want all to know Jesus and to live a perfect eternity with Him.
No, not everyone will make it to heaven, but would everyone want to? We know heaven is a place of peace and beauty and no more pain. Heaven is also where we will dwell with God and worship Him for eternity (Revelation 21:1-4, Revelation 15:4, Revelation 5:11-12).
If people don't love and worship God here on earth, is heaven where they would want to be? Heaven and eternal life with God are our free gift, but it is a gift each individual person has to choose for themselves. If we are not close to God now, we won't be for eternity either.
"For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life." John 3:16
This is the most popular verse for a reason. The key to salvation is simple at the root, whoever believes in Jesus will have eternal life. That belief, is in the heart and God knows if our belief is pure and genuine.
"Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven. Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?' Then I will tell them plainly, 'I never knew you. Away from me, you evildoers!" Mathew 7:21-23 (emphasis added)
These verses make clear the difference between sounding religious and having a personal relationship with Jesus. We can't just talk the talk, our actions are what matter. Our belief along with the way we live our lives matter. Being a good person apart from belief and relationship with the Lord will leave us falling short in the end.
The best way I have heard this described is comparing real friends with Facebook friends. For example, you are getting married, you said your vows, pictures are taken, dinner is served, and the cake is cut. Now it's time to let loose on the dance floor with all of your friends and loved ones. You notice a group of people walk in and make themselves comfortable at a table. You recognize them, "that is so and so, I am friends with them on Facebook." "I have never actually met them, why would they show up at my wedding???"
There is a difference between saying we believe and showing we believe. There is a difference between walking into church and hearing the message.
Loving Jesus at the very center of our hearts causes us to strip away all that is unclean and unhealthy in our lives. Not because we have to, rather because He changes us and our values and what is important in life. That change only happens when the relationship happens and is raw and real and undeniable. That is when we know Jesus, that is when we know we get to spend eternity with Him in heaven.