Ever heard of the Zeigarnick Effect?

The Zeigarnik Effect states that people remember uncompleted or interrupted tasks better than completed ones. Why is this good news for you?  Because if you leave them a little hungry and a little curious in fact very curious, they will not be able to let you go in their minds. This is what you want. You want to remain top of mind and there's no better way to do it and you arouse as much curiosity as possible and satisfy only 75% of it.