I'm at that stage in my novel where there's real progress and a good story going on, but I don't even think I'm more than halfway through. It feels like there's just so much more work. A LOT!!! Because then I'm going to need to go through it several times and I'm sure to do a lot of edit and revision. I want to take this one to the best possible place I can because I've never done that with my other novels. I work on it almost every day, but it just doesn't seem closed to finished and that is making me a little nervous. What if I get stuck? What if it's a stupid story because some of my best ideas turn out stupid? What if I don't finish? What if it's boring or I get bored? What if it doesn't make sense? What if it's a real embarrassment? I'm still writing and working on it despite possibly having a mid-story crisis.
Maybe take a little break from the story. That may sound counterintuitive (as you are eager to finish the thing), but maybe a little break will allow the story to seem fresh again when you return to it.
Add it to a long list of writing related failures and do something else? It's happened to everyone and nobody (that I'm aware of) has died from it yet.
You've got this! Try not to think big picture. Sometimes it helps me to stop writing after certain segments (25%, 50ish%) and go ahead and start edits on earlier chapters.
you are definitely having a mid-story crisis. it's okay. this happens every book. you just need to keep slogging--you're going to hit a point where the words are flowing again, you just have to get past this bit.
Maybe you´re asking yourself too many what ifs. What if none of them apply? Please do not misunderstand. If you have a good reason to believe that some of those issues is a problem, then you can do something. It just seems to me that a little more optimism could really help.