Often when I am working on mods I get some iconic mental images.
Gonna share one I had these days.
I was working on a dialogue system, and it is in the works but the gist of it is more or less like the following video:
While working on it, of course, I think about how it works, how it could work, and when I get problems I think about why it doesnt when it doest.
At a point I just stopped and laugh at myself because I could see me like this:
But I guess it could be worse:
Development in a nutshell: it’s either (relatively) smooth sailing or you’re banging your head against the wall because of that one thing that won’t work they way you want it to…
Here is a story from waaay back in the stone age, when I was rigging a humanoid figure for an animation I was working on. Not game development but I think it still relevant. 
So after days of building this complex combination of mesh objects, I was working on hierarchies for the articulation of the model.
When I tried a test animation the left foot would move as the left hand did,
this was not supposed to happen!
Long story short when I worked out what I had done wrong,
it was I had named the one of metatarsal bones too close to the name I had given one of the metacarpal bones.
So when the animation engine was calling for hand movement, it was grabbing the foot too.
LOL it had me banging my head on the desk for awhile.
The thing about rigging and animation is part of game development. Afaik.
It is similar, but I was working on an “animation” as in a realistic for it’s time “cartoon”.
unfortunately it was never finished and the project has been in limbo for years.
Project Limbo is sad. Specially if you had some big expectations on it.
I don’t think there is ever any smooth sailing for me (at least in game design or modding). When developing a new feature and it works right off the bat, I tend to over think it and test it to make sure its actually working.
… probably we all think that if that happens, is because something went wrong and we did not saw it rather than things actually working first try.
But what I think it is funnier still is that if we get something working, instead of going for the next stuff, we often keep making it more complicated until it doesnt. lol
I am currently developing an FPS shooter in Unity. Luckily for me, development is pretty smooth and all my written code works 90% of the time.
But I understand what you are talking about. Had other non-game projects that made me say more “wtf’s” than usual (was horrible code written by another company (projects were usually outsourced before)).
Or it works perfectly fine and you go on with the next stuff and then you suddenly break the perfectly fine working code. Then you have to rewrite it, so it works well together with the new stuff, but the code ends up 10x more complicated.
Always … lol