I would LOVE to be able to advise, but I just can't help twitching and every single year, without fail, I end up buying things I hadn't planned. I currently largely do this for two reasons: They are a bargain, or I just want to buy something off the cuff because it's nice and most of my sons presents are bought online (due to his tastes, largely), so buying something I've physically seen, without searching, is a lovely feeling - it's the thing I really miss from when he was little, traipsing round Woolworths, Toys'rus etc and just seeing things.
The other issue for me is I just love buying presents, it makes me happy and I can't help myself. I have curbed it a bit over the years, about 13 years ago I remember there were 60 presents under the tree, all for ds and all from me
. That has lessened as he's got older and presents get bigger more expensive yet smaller and he doesn't need a shed load of plastic toys!!!
So, it will probably get easier as yours age.
I guess my advice would be to do as much shopping as you can in physical shops, so you get more pleasure from it (opening a box from Amazon just isn't the same, is it?).
Then if you get the urge, and love the buying for people, like I do, if you don't want to go mad with presents for the kids, go present shopping for charities, childrens homes etc do the shoe box appeal and things like that. I know people mock, moan about and are downright rude to people who can't stop buying presents, tell us we're spoiling our kids etc etc but it's part of Christmas spirit -giving to others, so may aswell make the most of that positive thing and put a smile on the faces of those in need or with less, right? 