Disappointing God

(Where's the philosophical option for the entry type?)
 
Had an emotional breakdown today. Was practicing the piano, started banging real hard. Thought I broke a key! It's not sticking now so I think it's okay. I picked up the piano (it's digital - size of a keyboard) and threw it on the coffee table, then kicked the kitchen chairs around. Then cried, then kicked the chairs some more. Then put everything back in order.
 
Came to the realization that I feel bad because I know my mom feels disappointed about something. I can't change it, but it has to do with me, so I feel guilty or whatever. They say we tranfer our feelings towards our parents towards God, because as a child our parents are like god. I don't want to disappoint God. Which means doing anything less then devoting myself fulling to His service is unacceptable. Right now my health is so bad I have to focus on myself... in order to get better to serve Him.
 
Can we disappoint God? What disappoints God? How are we supposed to respond to God's feelings of disappointment? Would spending my life in a cute little home in the suburbs teaching piano disappoint him rather than choosing to give my life to service overseas? I don't want that look of disappointment - "You could've done better."