Even without the other problems, I can assure you that the vast majority of managers will think that a 80% done project is almost done. The truth is the remaining 20% is where you have to fit everything together so you revisit an rewrite most of the project. It's a different kind of work that feels boring because you already did those things maybe 3,4 times already. It helps to understand the phase of the project you are in, to reduce the frustration. It also helps to do something even very small, every day and focus on that. One day you will run out of things to do.