Pretending God Doesn't Exist
For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
- Romans 1:20-21 (KJV)
There really is no excuse, and at some level people just know.
Just look at how children grow. There's your miracle right there. 
But some people just choose some kind of life where there is no God (no accountability), so they can live out their sinful lives. They enjoy doing the sinful things, that God hates.
What people don't understand is that the Ten Commandments aren't just some leftover thing from Israel, but a necessity for a life with God. God doesn't want to see funeral after funeral, because we can't keep from killing each other. He needs us to abide in the laws of Love (because that's what they are).
The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.
- 2 Peter 3:9 (KJV)
God loves you, and is waiting for you.
If you're thankful for your life, why not invite Jesus, and ask Him to explain things?
Repent. 