He wants them to know that his death is actually a good thing, because the holy ghost can't come until he's dead. What to expect when the holy ghost finally does show up? Everything will be sorted into
He has a lot of other things to tell them, but they aren't ready yet. They won't be ready until the holy ghost arrives and shows them the future.
Death! Always and ever death. Millennial cults must suck. Jesus tells them he's leaving and coming back. This confuses the disciples, because apparently no one they know has ever been on a holiday? Or even to work? Jesus makes it even more confusing by saying that they'll weep while the world rejoices, then they'll be happy, too. Just like when women give birth to boys and at first it's painful, but then a man is born into the world. (v. 21) No word on whether the people who don't believe in Jesus will feel like they've given birth to a girl after the holy ghost comes back. But it wouldn't surprise me.
He promises that in the future, they'll be able to ask him for anything, and that he'll finally stop speaking in parables and will just say what he means directly. That will be a blessing indeed. The disciples swear up and down that he isn't confusing at all, and they fully believe that he's god. Jesus says that's good, because pretty soon they're going to be scattered and they'll need this memory to sustain them.