I hate waste. Always have. Everything seems useful to me, and throwing things away seems to be downright disrespectful to the luck that brought you each thing. And here in Oman, waste of water is on my mind every day. My professorial salary means I don't really have to worry about the cost of water, but every time I look out on that dry landscape, where acacias fight goats for survival, and only a few other tough plants and animals can make it in this aridity, I can't help but think of how hard it is to get good clean water. And all those people in the world, not just in the past, but in the present still, too much of the present, who struggle to get even a bucket of good water.
So here's one small idea. It'll seem picky and obsessive, but again, think of its cumulative effect. As you adjust the temperature of the shower, it's running and running. And so much water runs in even a second of shower flow. So plop a bucket underneath to catch this unused water. Works best if you have non-fixed showerhead on a flexible tube, but it can be wrangled in various ways. Then you have this bucket of water. Which you can use to flush a toilet once, or for all those times a kitchen spill, a mopping, a soaking, or some other situation requires a bit of utility water. It can sit around, it can be added to till it accumulates to a useful level. It won't breed bacteria and mosquitoes if you use it frequently enough: that's your call.
And it's a small thing, yes, but it's a remembrance, a daily remembrance, of what water is, to us all.