The term "water under the bridge" means to let things pass. What is done is done, do not dwell on it - let it go. When you hold on to thoughts or low energy emotions you are building a dam. You restrict the flow and new things cannot come into your life. You create pressure from the back log of water and you get tense and need to reinforce your dam. It is an uncomfortable way to live. Let it go, be free, let events come and go and flow.