Should I finish my PhD? I have one more year until finishing my PhD. I feel that I will have a mediocre PhD thesis, at best. I feel like quitting, and I had this feeling even from the start of the PhD. I felt even from the beginning that something is wrong and I should not continue but I continued anyway because I was very passionate about the subject that my thesis is supposed to be focused on. (Of course I did not get to do exactly what I thought I would do, but still... the things that I worked on belonged somehow to that area of study that I always interested in). I struggled a lot during these PhD years, and that's mainly because I did not get much help. Now I feel exhausted. I don't have any energy left to continue. I really feel that the reason I got into this situation is because people that were supposed to help me think very low of me... And they just left me to deal with my problems all by myself. Probably because they think I wasn't good enough to deserve much of their attention.

I have a few publications. In principle, I have all I need in order to finish. But somehow I feel like it is worthless. I am aware that it would be very stupid to quit right now. I don't know what to do. I don't know whether I will continue my work after the PhD graduation.
Your mental health is the most important factor in this equation. PhD's are hard, and demotivating, and exhausting. But the best PhD is a completed PhD! It sounds like you've got everything you need to finish, you just need to full together the threads that make up a thesis. 

Often people get most of the way through a PhD and have not taken a holiday in years. When was the last time you took a holiday or just some time off? 

Make a plan of exactly what is needed to finish. What are your publication requirements? Structure out what the thesis will look like and define any loose ends that need to be finished. Make a list of these things and plan out - week-by-week when you want these completed by. If the end is in sight, you'll find that motivation will return - like a marathon running who has hit the wall but can see light at the end of a tunnel. These feelings are so natural - almost everyone I know who did a PhD experienced it!

And with regards to you thinking your thesis is mediocre at best. EVERYONE thinks that! I'm not going to tell you that it's better (because I don't know). But statistically, half of PhD graduates wrote a thesis that is average or worse than average. I know mine certainly was! Who cares? If you do enough to pass, then it really doesn't matter. And the saving grace is that very few people will ever read and understand the thesis enough to work that out! 

You've got this! Remember to prioritise a good work-life balance as in the long run, it will serve you far more effectively than if you crammed for the next year!