Yup - stress and guilt are two different things. I might get stressed at having too much to do, I might not even like my job particualry (although it has imporved dramatically since I got a new boss), but I don't feel guilty about working!
I might want to drop from full time to 4 or even 3.5 days a week when dh starts earning again - although that extra time would be time for me - which I might on occasion use to spend extra time with ds (difficult now that he is at school) - and no I don't feel guilty about that!