Quince tree dying

Can anyone tell me why my precious quince tree seems to be dying?

 

Your plant seems to be unhappy - probably because it is in such a tiny pot. It would be better if you planted it in the garden so that it`s roots had a bit more space, and it needs a feed too I think.
It is not too clear from the photo, but is it a flowering quince - Chaenomeles ?

 

Thanks......The problem is that there isn't an actual garden as such, it is a terrace with pots. Should I transfer it to a larger pot?

 

Yes. You need to feed and water the poor thing. I would find a pot a little bigger than the one it is in now, and buy some really good compost - like John Innes. I would also cut it back a bit to about a foot high - just above a bud. See how it goes, and don`t forget to water it - make sure there is enough drainage though so it doesn`t get waterlogged. When it picks up and fills that pot with roots, you can put it in a slightly bigger pot. Good luck.