In the simplest sense, God was unsure of his actions. .
God did in fact go back on his original statements in many cases, however it was not because he regretted what he said in the first place or was unsure of his original decision. He did the opposite of what he announced because he forgave those who sinned and in other cases he took it upon himself to show his people how merciful he truly was. When God had stated that, "he regretted that he had made human beings," (Genesis 6.6) he sent down a flood on the earth, "to make an end to all flesh," (Genesis 6.13), by wiping out the human race along with all of the animals. However, he allowed Noah and his family to build an arc to fill with two of each of the animals of the world and to allow a haven for them to stay during the storm. .
God did not wipe out the entire human race, but instead was merciful on Noah's family and allowed them to live in order to repopulate after those who had become so sinful, perished. God had also made a promise after the forty days and forty nights where he swore that he would never again destroy every living creature. "When I bring clouds over the earth and the bow is seen in the clouds, I will remember my covenant that is between me and you and every living creature of all flesh; and the waters shall never again become a flood to destroy all flesh," (Genesis 9.13, 9.14, 9.15). By stating this, it showed that he wasn't unsure of his original decision but rather that he was merciful in allowing Noah and his family to thrive in a "new" world along with the promise that he would never again wipe out humanity. God forgave the human race by allowing these few chosen to continue with their lives and to repopulate the earth. He didn't regret his actions; rather he promised that it would never happen again because he became merciful towards those who he had affected with this flood.