What Will Happen?

This particular post is one that I'm considering turning into a short story. I'm not quite sure about the specifics yet, but I know where I want the general concept to go. Let me know if anyone has suggestions!

    They say never to never trust your tongue, when your heart is bitter. But the same is true of the opposite. You should never trust your tongue when your heart is consumed with happiness. When the pits of your life seem to be faded memories, far away and barely remembered.

    When your heart is so happy it seems fit to burst. Promises and dreams should be kept within. For what will happen when monotony returns? When once again your heart and mind have forgotten? But this time not the pits, but the peaks? When you can no longer remember what connected you to a person, that once seemed so engrained into your everyday?

    Into your everyday movements and thoughts. A time when you could barely imagine who you were before, and what exactly it was that you seemed to do with all of your time. When they were your time.

    Never trust your tongue when your heart is bitter, but never trust it when your heart is full of joy either. For what will happen to the person. The other, who seems to have still managed to hold on, even when you let go. So very easily. With seemingly little thought.

    What will happen?