Its not comments such as 'well done' that I'm wanting to hear, that's empty praise. I want the parts of my thesis that work to be identified, so I know what to keep.

I'm in my final year of my PhD - so have written about a third of thesis, but I think I've reached my limit of negative feedback. I've just had a meeting today with my supervisors to get their feedback on two chapters that I slogged it out for weeks staying up to midnight each night (and I've got 3 young children) - and all they talk about was the faults. And some of their comments or suggestions - I am actually offended that they think I am so stupid to not know. Their capacity to offer positive feedback has dropped off in the last few months - which is devastating as I near the end (hopefully) so one would think their should be more to praise.
I suffer from depression - so I desperately need tools to resist digesting their comments as personal attacks.
Whatever happened to the 'sandwich' approach to feedback (positive-constructive-positive)? - why does it drop off at graduate level? I know that when I am a qualified to supervise grad students - I will make sure I will always identify the positive features. Because we are still humans with feelings!
Any tips you are willing to share would be welcome.
Thanks
Louise