Unconcious self-limitation - You unconciously limit yourself, you don't know what you're able to do and therefore settle for something less, or something else, than what you could do.
Self-limitation by public opinion - You believe what others say about what you're able to do. And it's very common for other people to want to decrease your ambition, for some reason.
Result orientation - You do it to get a result, which means you will stop if you get a bad result, or abandon the project quickly if the process isn't fun and you don't get immediate results.
Doing it for someone else - You do what you think you should do, or what you think other people want. Which could work, but rarely works in long term because it isn't necessarily what you think is fun to do.
Sensitivity to criticism - You change your mind based on what other people think. So your project is doomed to fail if you get criticism, which you often will if you try to create something unique.
Abandonment (and/or "toxic project starting") - You either grow tired of your current project, or get too excited about a new one (these two often coincide), which leads to you abondoning your current project.
Over-ambition, or scope growth - You plan unrealistically, without regard to your current ability. And you don't know how to limit the scope, kill your darlings and stay realistic when you realize how much bigger the project is than you thought, so it explodes and you never finish it.
I would also say that procrastination is a big obstacle in all parts of a project. But procrastination isn't unique to creative projects, it feels like a pretty obvious part of being a human, so... You probably already know about that one
Unconcious self-limitation - You unconciously limit yourself, you don't know what you're able to do and therefore settle for something less, or something else, than what you could do.
Self-limitation by public opinion - You believe what others say about what you're able to do. And it's very common for other people to want to decrease your ambition, for some reason.
Those two are the most common obstacles for getting started, I believe.
Result orientation - You do it to get a result, which means you will stop if you get a bad result, or abandon the project quickly if the process isn't fun and you don't get immediate results.
Doing it for someone else - You do what you think you should do, or what you think other people want. Which could work, but rarely works in long term because it isn't necessarily what you think is fun to do.
Sensitivity to criticism - You change your mind based on what other people think. So your project is doomed to fail if you get criticism, which you often will if you try to create something unique.
Those three I would say make it difficult to establish a process that works in the long term. Which is need if you want to ever finish your project...
So the biggest obstacles for finishing a project are, in my opinion:
Perfectionism - You are never satisfied, so you will never relase anything finished.
Abandonment (and/or "toxic project starting") - You either grow tired of your current project, or get too excited about a new one (these two often coincide), which leads to you abondoning your current project.
Over-ambition, or scope growth - You plan unrealistically, without regard to your current ability. And you don't know how to limit the scope, kill your darlings and stay realistic when you realize how much bigger the project is than you thought, so it explodes and you never finish it.
... and, over-ambition almost always happen, no matter how small you try to make the project.
I would also say that procrastination is a big obstacle in all parts of a project. But procrastination isn't unique to creative projects, it feels like a pretty obvious part of being a human, so... You probably already know about that one