Donna and the Doctor have completely different ideas of what a vacation should be. He wants to be off visiting the planet’s tourist attractions, but all Donna wants to do is relax, lounging by the pool, maybe going to the spa.
Travelling with the Doctor is fun but exhausting. The past few months she’s been run off her feet, literally. She hasn’t run so much since PE lessons at school. It’s alright for spaceboy, he’s got energy to burn, but Donna needs a break.
Let him chase across the plant looking at waterfalls if he wants. Sunbathing is much nicer.