I've already touched on the topic of buying into minimalism, but let me expand on that.
Sometimes I get into this weird frame of mind where I think, "I should replace what I have with something else." I'm not sure what triggers it - I suspect it may just be an impulse to buy more stuff. In any case, I think, "I should buy a new thing that limits me even more." For example, I considered buying a Netbook to limit what I use my computer for.
The problem with this approach is that it doesn't attack the core issue. You're not mindfully reducing, you're trying to buy something that will do it for you. Instead of confronting the reduction and dealing with your issues, you're sticking with the mindset of "the new thing will fix my problem" that minimalism usually works better without.
Instead of pushing yourself down by buying a new product, consider the usefulness of the tool in the first place. I wanted to get a new eReader with less features. Here's what I said to myself earlier this week: "You don't want these extra features. Do you really need the eReader at all?" Then I had to justify to myself, yes, it's my entertainment device, it's the best thing since pumpernickel bread, and so on. Then I'm not so worried about the features I don't use, because my mind is thinking on the broader, bigger picture that we lose when we analyze the minutia.
You don't need a smaller wallet to convince yourself to carry around fewer cards and less cash. You can do it without a new wallet. It's not about the new product, and it's not going to magically make everything better. It's about you coming to terms with what you want and how you're going to get there. You can do that without a trip to the store.