I did it with my wife when we visited Croatia ages ago. We only planned the flight there (to Split) and the flight back (from Zagreb), and we had to figure out how where to sleep and how to get everywhere. We visited the big island at the coast near Split, we visited Dubrovnic, the big nature park in the middle of the country. It was great. Not hard to do at all.

Though I expect some places outside Europe it might get a bit harder.