The thing that makes me happy about my PhD is:

I get to go out and play in the sun all day (though I burnt my neck today ) and have the odd beer, all in the name of science!

= sunburnt smiley

the thing that makes me happy is

I'm halfway through!!!!!

(and I had lots of positive feedback recently and a number of people very impressed with my work including a remark that I could finish in 2 years if I wanted - sadly not from one of my supervisors).

that it will end one day! with or without the degree!!!!

I am happy with my PhD today because it enabled me to stay in my pyjamas until 2pm, even though I started "work" at 8am. How many jobs can let you get away with that sort of carry on?