No thanks

Had a super fun night last night with sis, enjoyed a sappy romantic movie, ate some delicious food that took me a solid 3 hours to make, and slept a great restful sleep. Now - having woken up, made coffee and done the dishes, I know I should continue to clean for the dinner party tonight and then go for a run and then go volunteer but all I can muster is a polite, "No, thank you". So often I hate doing the things that will make me happy, make me feel better and improve the world around me. Why is that? Why do we shun responsibility and obligations that truly do benefit us physically and emotionally? Justification upon justification - let's see who wins today? Me, or my head...