That is why
The apostle Peter said
"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ."
When the people heard this, they were cut to the heart and said to Peter and the other apostles, "Brothers, what shall we do?"
Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.
The promise is for you and your children and for all who are far off—for all whom the Lord our God will call." Acts 2:36-39.
Everyone irrespective of who you are has sinned. Sin defined is,
"Sin is anything that contrary to the will of God or doesn't express the holy character of God, in word, in deed and in thought.
Sin, then, is to transgress those boundaries God has set for us or to miss the target He set for us.”
Thus according to the definition all have sinned. The apostle Paul saying,
"for all have sinned and fall short of the glory of God," Romans 3:23.
"But God demonstrates his own love for us in this: While we were still sinners, Christ died for us." Romans 5:8.
The apostle John writes,
"If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.
If we claim we have not sinned, we make him out to be a liar and his word has no place in our lives." 1John 1:9-10
God knows we cannot live a life good enough to get into heaven that is why He sent his son to show in human terms how far He would go to help us to get into heaven.
The key however is believing that Jesus is the Son of God and that He died for your sins. Do you believe this?
Please think about it.