But vs. And

Son, I love you so much, but I want you to clean your room.

Think about it: "but" negates everything that comes before it. It is an adversative conjunction, that is, it connects opposing phrases.

Use "and" - it is an additive conjunction, connecting phrases, one affirming the other or one building upon the other.

Son, I love you so much, and when you clean your room, it makes me so happy. 

If you have to use to use "but," start with the negative.

Son, your room is an awful mess, but I still love you so much.