According to the author of the book of 1 Chronicles, God is telling someone, "I have been with you everywhere you go, helped you win over all your enemies, and made your name famous like the names of great people on Earth."
1 Chronicles 17:8: And I have been with thee whithersoever thou hast walked, and have cut off all thine enemies from before thee, and have made thee a name like the name of the great men that [are] in the earth.
God regrets making Saul king, indicating a change in decision and support, which contrasts with the unwavering support promised in 1 Chronicles 17:8.
1 Samuel 15:11: It repenteth me that I have set up Saul [to be] king: for he is turned back from following me, and hath not performed my commandments. And it grieved Samuel; and he cried unto the LORD all night.