Hi Ellain, I get like that sometimes too, worse, in fact. I call first years the 'liittle bas*ards' in my mind as a term of endearment towards the end of the autummn term. Last year I had a particularly rotten group and I swear I had nightmares about one or two of them.
But I also love them a lot of the time too. I have caught myself refering to the first years as 'darling' a few times, the way my aunty does with me, usually after Christmas when they have become house trained and lovely - I have to make a real effort not to. Luckily I am a woman, so maybe that's not as bad as if a bloke did it...
I find undergraduates, especially first years, are a lot like toddlers. Horrendously demanding as they test out boundaries and your patience, but also wonderfully endearing as you watch their charcaters and subject skills grow.
My friend has been lecturing for 10 years and she 'hates' them all... Can't bear them most of the time. But loves them really.
I think a lot of this has to do with understaffing. I'm sure if I had less students per pound I am paid I could attend to them properly and they wouldn't stress me out so much. Don't feel guilty, you're just coping the way you have to. It is tough to handle so much responsibility in under-resourced conditions.