"Sorry, babe, but it's my ONE YEAR ANNIVERSARY since I stopped cigarettes and that is a HUGE milestone for me. I work hard, I put away half my paycheck toward the car. Let me have this one present to myself to celebrate how hard I've worked toward this goal.
Would YOU like something, too, sweetheart? Would that help make it easier for you? I'm not going to argue with you over this because I deserve my award to myself but it's no problem to share my joy with you because I love you."
Try it.