As someone who just bought curtains (and a new duvet and a shoe organizer and picture frames) about 2 months before her lease was up for renewal, I IDENTIFY SO HARD WITH THIS. I know I get used to the way things look and forget about how they could look — and, more than that, how they probably should look.
It definitely helped when I spliced out a section of my budget specifically for home supplies/clothes/Adult Things. When I don’t spend anything in that category for the month, it makes me think twice about whether I should be. It also makes me feel less guilty about spending ~$100 on assorted home frippery because it’s in the budget dammit!