Then Noah built an altar to the LORD and, taking some of all the clean animals and clean birds, he sacrificed burnt offerings on it. The LORD smelled the pleasing aroma and said in his heart: "Never again will I curse the ground because of man, even though every inclination of his heart is evil from childhood. And never again will I destroy all living creatures, as I have done. (Genesis 8:20, 21)
God's promise of not to destroy all living creatures again has stood the test of time and has been true to this day.
One family of 8 survived the flood because God found one man to be righteous in that generation. The Bible says, "Noah walked with God."
When everyone around is going astray don't take that as a clue that everything is lost. The Lord's eyes are on them whose hearts are committed to him.
The prophet Elijah thought that he was the only righteous man in all Israel. In his self righteous attitude he told God twice the following things:
"I have been very zealous for the LORD God Almighty. The Israelites have rejected your covenant, broken down your altars, and put your prophets to death with the sword. I am the only one left, and now they are trying to kill me too." (1 Kings 19:10)
God corrected him by telling him that:
Yet I have left me seven thousand in Israel, all the knees which have not bowed unto Baal, and every mouth which hath not kissed him. (1 Kings 19:18)
Perhaps you may think that you are the only one left whose doctrines are all right. Good for you, but God has seen many more hearts that are living for him though their doctrines may not be perfect.
Come to think of it, all the 7 people in the ark besides Noah perhaps were not righteous as him, yet God did not forsake them. Your spouse or children or parents may not be as spiritual as you are, yet God doesn't condemn them. So have a heart that can accomodate those who are of the faith, but not as strong as you are.
We who are strong ought to bear with the failings of the weak and not to please ourselves. (Romans 15:1)