Don’t leave any loose ends in your novel
When I am reading a book it really gets on my nerves when I finish the novel and I think back over the plot and there are some sections which have not been fully finished off. For example, the last book I read, the character’s aunty died and there was no closure, ie. No funeral and no grieving for their loss of a relative, etc.
It is important that you leave your reader feeling satisfied that the whole story has been told. If you leave any unintentional loose ends, like the one I mentioned above your reader will be dissatisfied and unlikely to read any of your books again.