I too am bad at decision making, when i am utterly excited about getting something. Recently i bought a note 2 out of sheer excitement, used it for not more than a month as it was too big for my liking. Sold it off at a minimal loss and got the S4. Now i am satisfied atleast for now.
So, yes i dont think much about "should i buy it or not?"
Coz frankly speaking the gadgets we all have can suffice and survive easily for the next 10 years with the way we use it. (Eg.: I use all my phones in cases and screen guards - so years later they are immaculate like they were when bought

)
It's the urge to explore and grow that takes over when moving to an upgrade or heck just an exchange. Don't ever let this curiosity end - this is how you will grow in life. At the same time, dont get obsessed with it either. Yes plan your finances, but when it comes to pampering yourself and family, just go for it.
I have one funda - I always go for things that i can afford. Anything beyond that is what i aim at.