Feeling guilty because I can't work late - anyone else in this situation?

[Gemmasmummy]

I work part time (3 days per week) in a publishing company. A childminder looks after my 2 year old daughter and the contract is for 8 hours a day, 3 days a week, 8.30 to 4.30. My boss has asked if I can stay late to do some urgent work. I could ask my husband to pick her up but it would be going out of his way and I might not get to see my daugher before she went to bed. Other colleagues without children can work late sometimes but it's not fair to always expect them to do it and I wonder if they feel resentful towards me. So my boss is going to stay behind and do the work. I feel bad that I can't be flexible with my hours but what can I do? I'm only paid part-time wages and the company agreed to take me on on that basis (I was full time before I went on maternity leave). Can anyone advise?

Yes, me! I'm full time, but need to leave at 4.30pm on the dot to get the train home because dp then works in the evening. I'm a manager and most of the other people working at my level (sounds arsey but you know what I mean) work later than me, and I feel really bad swanning off at 4.30pm. I get in at 8.30am and never take lunch, but still feel bad. So I end up blackberrying all evening and doing stuff at home - but still feel guilty..!