It's interesting to think about this in light of the first plague. Then, God turned the waters of the life-giving and sustaining Nile into blood as a way to show that God was in control of life. Here, the bitter waters prevented the people from drinking, and so God turns the water sweet, so the people can enjoy the life-giving and sustaining water in the desert.
As with so many things in life, bad things from the past are redeemed, because God is at work, setting up patterns of redemption in our lives, showing us the restorative power of the Gospel. Have you ever had something bad happen in your past, only for something good that you never could have expected come out of that thing? I think about all the struggles I had with engineering in college, to the point where I eventually dropped that major and ended up studying religion and accounting, two skills that sustain me at this point in my career. Not what I ever expected -- but where I looked at things with disappointment, there was opportunity in the threads that God was weaving.
This is the power of the Gospel. This is the message of Good Friday -- the ultimate tragedy, and yet from that, God draws the ultimate life-giving and sustaining miracle. So let us not despair. It is right to mourn some things in life, and yet there is always hope in the midst. Sometimes it is hard to see it, and sometimes we are too broken to look. That is the power of community. They come sit alongside us and help sustain us, and when the time is right, they help us find the hope to move forward, to find the life sustaining power of the Holy Spirit at work redeeming the broken things in life and making them beautiful.