There's one thing that I think it's more than okay to spend on. In fact, I can't spend enough on this! It's my health. Okay, that's how I wish I felt. Sadly, I sometimes delay health spending that I need (not critical, but still). That has backfired in the past. In grad school (sans dental insurance) I waited a year to get my teeth cleaned. For most people, probably not a big deal. For me, I knew it could be bad. And it was. I eventually had pain and was then forced to go get a cleaning. However, because I had waited there was so much plaque they had to do it in two visits, hence costing double the normal amount.
So I realized finally hey, I have health and dental insurance. That is a luxury in many parts of the world. I should take advantage of this. So I'm going to the dentist, eye doctor, a therapist (mental health is important too), possibly the acupuncturist and the orthodontist. This in reality shouldn't cost too much, due to my insurance. However, the orthodontist could be a couple of hundred dollars and the therapist could be several hundred dollars a month. I'm forcing myself to spend this money, because there is nothing more important to spend on. This is what my FSA is for, so it's nice to know it will be tax-free money at least. Now I wish I had dumped more in there.