You need to take a step back and chill out, and
after that just have a think out of the box of how you can solve it, there is no
point worrying about failure after all some of the greatest minds have failed
more than once and tried again. If your in the 4th year then don't worry about
friends and socialising complete the PhD its more important you can socialise
next year I myself have had this problem where no-one calls me anymore because I'm
always busy but its the future that counts and the friends you think you have
normally have a tendency to disappear real friends will stick around and
understand you are doing something important. You might not be getting enough
sunlight and that's why your depressed i currently have a friend who is having
this problem take regular breaks outside and i think she takes those magnesium
tablets too for women's health. Don't stay up late go to sleep ok! Nothings worth
killing yourself for so relax! chill out! and treat your research as a puzzle
game that needs to be cracked! :-)