I have sinned
Romans 3v23 says "all have sinned and fall short of the glory of God". That means that every human being has failed to meet the perfect standard of God's goodness and righteousness. We have failed because we have done things our way, not God's way. We have disobeyed His instruction which He wrote in both the Bible and in our consciences. God's law is like a pane of glass; it's either broken or it isn't. It's no good saying "I only lied, I never stole". James 2v10 says "For whoever keeps the whole law and yet stumbles at just one point is guilty of breaking all of it". Whether it's murder or whether it's just a 'white' lie, whether it's adultery or just jealousy, every sin keeps us from meeting God's standard and has both consequences and penalty!
The consequences of sin can be numerous. If we lie we can get caught and break relationships & trust. If we steal we can be caught and prosecuted. But the most serious consequence of sin is that it separates us from God and from the relationship He created us to have with Him. Isaiah 59v2 says "But your iniquities have separated you from your God; your sins have hidden His face from you, so that He will not hear."
Have you ever wondered why God feels so far away?
Even more serious is the penalty for sin. Romans 6v23 says "For the wages of sin is death" i.e. death is what you earn from sinning. Not physical death since that is inevitable for all of us. It's the ultimate statistic; 1 out of 1 die. The Bible is referring to spiritual death, that is the assumption that we are more than just physical bodies; that we have a spirit or soul which persists after our bodies die. It is unclear exactly what it means for us to face spiritual death but it is clear that it is the opposite of God's desired plan for you and I which is that our spirit goes to dwell with Him forever in His presence; what the Bible calls heaven.
So we all have a big problem. We have all sinned and because God is perfectly just, this sin means we must all face spiritual death and eternal separation from God; what the Bible calls Hell!
If you're unhappy about this you'll be pleased to know that because of His great love for you, God was even more unhappy with the situation (2 Peter 3v9). Cue point number 3.