Here's some good food for thought from the UN's World Water Day (if you'll pardon the pun):
In addition to the very important link between water and food emphasized above, I'll add that wasted water also means wasted energy. Typically a very large share of a municipality's energy use goes to pumping water. Stop and think about it.
All of the water that comes to you (unless you live in an uncommon place where water comes from an artesian well) had to be pumped before reaching your faucet. For those of us on municipal water (in almost all cases), it's not being pumped to our homes, it's being fed by gravity from a water tower or water tank at higher elevation. Using gravity to deliver protects water supplies from fluctuations of use and from power outages. But, the water needs to get into those tanks and towers somehow, and that almost always involves a lot of pumping.
We in the Northeast are lucky to have an abundance of potable water, but wasting it still has consequences even though it is a plentiful resource. So, swap in a low flow shower head, and if you haven't got a low flow toilet, replace that too (but do some research first, as some do the job much better than others). Think about your diet, including what you drink, too. (See the image below). Take shorter showers, and more importantly, figure out what your community can do to use less water and how you can help. Then help.