Yes, always have to know where the story is going to end - or generally where I want it to end - it will be changed, nuanced, and other layers may be added in during the rewrite process, but going into writing a draft I know my ending. Sometimes it even helps me to work backwards from the ending to fill in earlier scenes leading up to the ending. My ending is my "true north" - it's where the story must go.

Knowing the end of your story is one of the single most important breakthroughs in the process. Since everything LEADS to that, it figures that the end, in effect, DEFINES the arc of the plot. Looking at it psychologically, it is almost always the terminus point of the Protagonist's journey, events in the External World that create the biggest challenge [Final Struggle] infused with meaning arising from the Internal World, not just some gratuitous occurrence, but one that specifically ties into the P's transformation. Usually at stake is a psychological question surrounding the P's identity: Who ARE you? An existential question that can only be answered by the combination of how they have changed manifested in action in the culminating Plotline point. So yes, the ending is HUGE! And, Lisa, working backward is always an option when plotting the story.