Why do I still struggle with lack of naps??

The day spent at my parents was going fine until afternoon nap time. After an hour of laying Poppy back down from standing up, shooshing, switching the mobile back on, etc etc I'd had enough. But it still upset me. You'd think after 11 months I'd be used to it. It just feels like whenever I deviate from our usual routine where she has a nap in her own cot, it ends in an afternoon of tears, me feeling like shit, a grumpy Poppy and me wondering how I'll get through to bedtime. I was so annoyed at her when I'd driven home and she woke up when I got her out of the car, I just wanted to get away from her! Arghh! I;m sure that makes me an awful mother. I tried telling my hubby that when he gave me my mothers day gift early, to cheer me up, I don't deserve a mothers day present...The stupid thing is I know I'm over-reacting but I can't stop myself descending into the vicious spiral. Oh well you live and learn.