One of the biggest problems writers can have when starting out is to not have a real ending. By this I don’t just mean a novel that requires a sequel to finish telling the story (also a bad idea by the way) but a story with no real resolution.
You should resolve at least one major thread by the end of the book, if others are open that is fine, but you need to close at least one. In fact you SHOULD not close all of them. You want your book to feel organic, like the characters are acting and decided things, not that actions are happening and your characters just happen to be nearby. In real life you never reach a point where everything is resolved.
Think about the end of the World War Two, the war was over, and everything was much better. However it led to the cold war and a great shifting of power in the world. Nothing in real life ever just ends.
That said, you need to have enough resolution that the book feels over, even if the overall story is not.
This applies, in part, to minor threads as well. All the minor threads should move, they should be going somehwere, or they are not worth pagespace.
To keep things moving it helps to have goal posts, touchstones you can use to make sure you know should be happening when. For example:
Joe and Mary, meet and hate each other.
They admit they are very attracted to each other and have sex.
They start to live with each other after spending time together.
They get married.
The plot is always going somewhere, and you need to know three and four to write one. You need to know the end before the start can really work.
Now you may not know the end in the first draft, just don’t be afraid to go back and revise and you’ll be fine.