Ally wrote:I think it's just that I'm concentrating too hard on my technique! Although I do find it's worse when I'm trying to increase. I was trying to make a Mario mushroom, after increasing I was meant to have 60 sts, and for some reason I had 48! I was so sure I had been counting right too!
It's very likely that's what's happening. Since you're making a Mario Mushroom I'm going to assume you're working in the round, yeah? Stitch markers can really be your best friend the first few times you work in the round even if you just place one at the start so you know where the circle ends.
Getting used to increases, especially dramatic ones like those in a Mario Mushroom, is a bit of learning curve until you get used to/confident with the concept. I can't tell you how many rows I've undone thanks to missing an increase or two. My best advice when working with increase heavy rows is to mark the beginning of the row either with a stitch marker or even a bit of different colored yarn so you know where you started, and then double check your stitch count after every few stitches to make sure you're on track. It will add time to your project but it's not a race, and it should help whatever stitch you're doing become more natural as you can't stress about it quite so much as you have to start and stop your work often, forcing you to get comfortable with it.
Without watching you in person I'm afraid that's the best help I can offer, hope it helps!