We rose early to drive the two, three hours to hike Glymur Falls in the only day forecasted to be sunny on our trip. It meant doubling back the way we came, but fortunately we were booked for two nights in the South.
I was dragging, but optimistic to see the second (?) highest waterfall in Iceland. Even before we got to the trailhead a smaller, charming waterfall demanded a pit stop. This would be a theme on our trip, so lucky! Sweeping swooping green slopes gave way to a waterway on one side.
I drove for part, getting to learn new roundabout conventions first-hand, including a gauntlet of six consecutive one. Nothing like rapid repetition to help you work things out in your brain.
On foot: after some flat, low-brush terrain, past tiny sprawling civilizations of mosi over rock, and Vottahellir cave (full of legends! And a plaque!) we got to an icy stream. The decision to cross at a wider but shallower point turned out well. I was very glad to have bothered to pack hiking poles mid-stream. What was icy cold turned to pins and needles of pain then, and my brain got to tell my legs to keep going, and faster(!) while my legs threatened to stop working from thinking they were on fire, and to give up all function. 
When I was a kid in Minnesota, I went to this one summer day camp where they taught us, among other things,* to waterproof regular matches by painting clear nail polish on them. Years later living in Seattle, I diligently painted and dried each match this way. That’s the Dahlia Lounge matches you see in the picture. Then for about 4 years I brought them with for car camping and found they were annoyingly hard to strike, delaying my access to delicious and/or experimental dehydrated camp meals. I ended up defaulting to regular ones, like the ones above from Fish and Game Hudson here. Conclusion: you could also always go for survival matches like the ones above, or regular ones in a ziploc bag. Sometimes DIY is overrated.
*I vaguely recall them also teaching us to cut radishes into rose shapes…