It's a long scroll down to the bit that responds to the title:

> Travelling under 24 hours of daylight definitely changes you. At first it feels like a gift; endless time to explore, hike, fish, and wander without the urgency of sunset. But then sleep deprivation creeps in and your sense of time warps. Meals happen whenever you remember them, not because of hunger.

> The mental effect is harder to pin down. A constant day gives you freedom, but also restlessness. I found myself craving darkness, craving the reset of night.

I had a few weeks cycling and travelling around Iceland in the middle of summer. It was great. I didn't really experience any downsides at all.