“By the morning brightness” Allah swt is giving a oath. It’s a new day, don’t look at the past, look at the present. There are new opportunities and positiveness.
“And by the night when it covers with darkness”, it’s the night where it’s calm. Both ayats contrast eachother. Stop feeling that you are not worth anything. Allah swt does not hate anyone. He loves the one who repents to him durning the night. Allah swt loves his servant more then a mother to her child. Every Muslim believes in the Prophet.