For buying a house, I latched onto the idea that I needed a 20% down payment so I wouldn't have to pay for mortgage insurance so I was trying to save like crazy. Meanwhile, the property values were going through the roof and I realized that I'd always be chasing that 20%. I sat down and ran some numbers with a mortgage lender and that made everything a lot clearer. I could have bought a place two or three years earlier and been making money on the property value with essentially the same amount of savings. Probably not true in every area though.
Kind of the same thing with grad school. I needed a break from school after undergrad, so I took a few years. Work experience is great, but I hit a career ceiling in terms of being seen as "qualified" for certain opportunities. I should have just gone back and started taking classes much sooner.