MY advice:
~Find an ending you want~
~Find a theme or a message that pervades the text~
If you realise these two things-
one, the end goal that you are working towards;
and two, the purpose for writing-
then you will produce a much more directed and focused piece of work, that will generally be of a higher quality because it adheres with these two factors.
In life in general, things tend to be better when working towards a goal, or an aim- attempting to achieve something always allows an individual to reach their aims than if they are not focused on what they want.
Once you realise where the story ends up, and what you want out of it, the book should almost fully form itself between the beginning and the end.
Hope that helps.
Phsy xx