There are two teacups on the table in front of your tamagotchi. Use only the A and B buttons in this game.
If one of the teacups appears to be taller than the other one, that means it is raised. (When it is not raised, it appears to be like a coffe mug. When it is raised, it appears to be like a coffe mug standing on top of a little block.). If the cup on the right side of the screen is raised, press the B button. If the cup on the left side of the screen is raised, press the A button. Sometimes both of the teacups may be raised. When that happens, press both A and B at the same time. If you do not press them at the same time, you will lose the game.
Taking to long on this game or pressing the wrong button is what will cause you to lose.