I'm pretty much the same way online. When I don't have enough funds to buy an item, and in my mind "what if I wait till pay day, will it still be available? what if they sell out, and don't restock" - many times I have to make the difficult decision and wait, especially when I have to buy my medication, it always comes first.
[took me a while to respond, I have been for the last couple of hours looking on Japan Video games, Troll and Toad, & Toy Whiz, looking at Pokemon merchandise, trying to decide what to buy in May - I have all my shortcuts in a subfolder I called "purchase plan" items I want to get first]