When I finished, I was sweaty, thirsty, exhausted and a little dizzy. I had a slight headache, a strong sense of accomplishment and relief, a confused appetite (hungry? no? yes?) and a moderately impaired decision making ability. I enjoyed having done it, even though it was painful and difficult at some spots, and I very much liked how it felt to be done. Both the 1/2 marathon and the thesis defense were harder than I expected... and in both cases, I was able to finish with my head up.
Also in both cases, my satisfaction came from having run/worked well, not from the time/grade I received (I didn't actually get a grade on the thesis yet - it'll be interesting to see what grade I get. It could totally go either way).
In the end, it was a lot of fun. The thesis committee asked some very pointed, tough questions, and all I can say is "Dang, I like a good fight." I enjoy being challenged and pressed and forced to explain my position.
And holy cow, I'm so glad to be done.