Money is probably the only thing that you could always argue there was a "better" use for, typically after the fact.
Darn! I should have bought DIS before earnings!
Darn! I should have bought this TV after they put it on sale!
Darn! I should have saved more!
Are we serious here? My formula has always been, $17,500 my 401k, $5,500 in IRA, have 24 months emergency fund, no car notes, and perhaps only a mortgage at a low interest rate. I can't tell someone they need to have all of that done before they can "logically" able to take a vacation to Disney.
Even in my situation, there are always "better" uses for money than taking a trip to Disney or any trip for that matter.
You do at some point have to enjoy life. Saving for college, investing, and retirement are important, but if you do nothing in the meantime, what are you doing?