I'm lucky, being a minimalist by nature and always been a saver (working for a month and saving nothing that month would make me sad), so tend to buy only what I need, mostly. I do tend to overspend on some items though, such as cars in the past and clothing, oh, and computer stuff probably too. All of which gets used but could spend less on, but are pretty much the only things I "treat" myself on.
People should think more about what not buying something means in the longer term. Saving an extra lets say £10k could mean retiring a year earlier. Might not care about that now but aged 67 or whatever you could think "if only I saved a bit more I could not be doing this **** anymore".
I moved into a decent sized house and had hardly any furniture for the first few years until I decided exactly what I needed. Even the TV was put on an empty cardboard box