If you can afford it, have no debt, and have enough in the bank to retire on, I say "Go for it!"
If you don't, then stop.
One thing that I did to get rid of any GAS I ever had was I bought my first set of Pork Pie USA Customs. I loved looking at drums, but since I got EXACTLY what I wanted (even the finish was exactly what I wanted), I didn't even give another drum set another thought. I've accumulated more sets now, but it's been on an "as needed" basis. Same thing happened when I bought my Taylor guitar. I've not even THOUGHT about buying another guitar, and that was about 8 years ago.
Buy once, cry once.
Also, whatever you buy, pay in cash, not on a card. The reason is psychological. According to Dave Ramsey (a finance guy I watch/follow), when you pay in cash and you are physically counting out and handing over dollars, there is a response in the brain that is very similar to the signal of pain and discomfort. This is why people who pay with cash spend less...because it freakin' hurts! When you use a card or order online, those pain receptors aren't firing; therefore, it don't hurt as bad. Believe me, when you have a fist full of hundreds and you are getting ready to buy an instrument (or anything), it'll make you think twice.
In addition, by buying something for yourself, you are taking away something that you could use for your family. Best of luck!