I'm doing my PhD in mathematics (Germany) for four years, and I have agreed with my supervisor that I should finish within the next half a year.
I am not very confident that this is a realistic perspective. I have worked on various things in the past four years but have hardly been successful in any of these endeavours. Apart from actually developing results, it was already hard to find good questions to work on. My supervisor has made it clear that it's not his role to help me find good problems to work on.
Anyway, I have been working on a particular project for three years. I have some results, but I would them deem quite disappointing for the time I invested. The project involved some algorithmic developments, which ate most of the time; but certainly, no one will award me any degree for having developed and implemented some algorithm that's neither particular efficient, nor particularly interesting, nor about which any theoretical properties I can prove. To summarize, my results are very, very weak (I'd say much less in mathematics than what I did in my Master's).
Thus, I'm constantly asking myself: "what could I write my thesis about then?"
When I approach my supervisor and tell him that I don't estimate my results by any means sufficient for graduation, he tells me to stay confident and to continue working on my project. I have started suspecting that telling me to stay confident is just the way of least resistance for him, which allows him to avoid an uncomfortable discussion.
I already noticed that my sleep quality, ability to concentrate, to enjoy pleasant moments or to optimistically look into the future have drastically deteriorated, and I am asking myself almost every day: "what could life look like when I actually have failed?"
How could I deal with the situation?