Genesis 9:16 And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth.
There was a world wide flood. It destroyed the entire earth. It covered the highest point on the earth and the water was over the earth for months just like the Bible says. The effects of that flood give us much of the topography that we enjoy today. That flood made possible even the oil that we use to power many of our machines today. The flood was very beneficial for us today.
However it was extremely destructive to all that lived on the planet then. God promised that it will never happen again. He gave His Word that there would be no more world wide floods. There will be massive floods but they will be localized, contained to an area.
God makes promises. His promises are true. He keeps His Word. We can depend on Him, His honesty and integrity!
So when you read about His promises about your salvation you can believe those too! When you read about His coming again, you can believe that too! He is a God of His Word!