These apply to solo leisure trips to far-flung destinations:

Spending too much time in the morning psyching myself up for the day by reading the guidebook, even when I've read those sections already and have the day planned out. It may be only 15 minutes but that's 15 minutes I'm not spending exploring.

Staying up a little later watching a trashy rom-com or something that happens to be on in English (Star World in Vietnam, for instance). I have to remind myself that it's OK to relax a bit and not be culture-immersed every moment!

Seth