I work 24 hours a week so I can do school run. I like it that way. I don't work on a Friday so I can visit friends and eat cake-- do house work, food shop and walk my dog. I run, I love running, I am in a club, I do it daily, I therefore have no time nor desire to increase my work hours/further my career/clib the corporate ladder. My old boss understood this. My new boss however is very corporate and extremely driven and I can not tell him I lack ambition 
Any suggestions of how I can fluff it up a little?