I go through stages.
Some times I think to my self, I am happy with how the car is. Im not going to spend any thing on her unless its to fix a major fualt/put fuel in it.
Il then be on the forums scouring through, and see something come up at a price I would be happy to pay. That pretty much f**ks up the whole plan for not spending money. Everyone knows then when you buy one part, your probably going to need to buy another 5 bits to make it fit/work. It keeps spiralling on from there really every month!
Not to mention I usualy have times where I know exactly what I want and how I want to do it. I usualy just go out and do it and spend what ever I need to spend in order to achieve it. Be it immediately, or over a long period of time.