There is a Tide
"There is a tide in the affairs of men..." an ebb and a flow, a waxing and waning, a bright side and a dark side. It is a tide of moods, not the extremes of mood witnessed in a manic or depressive episode. Rather, it is the continual tide of moods that ebb and flow and with which all humanity is familiar. But for us high tide is much fuller, and low tide more desolate, than for most people.
This is the natural order. The tide comes in and the tide goes out. When the tide goes out we wallow in the mud and slime at the bottom. When it returns we bob up and down with every passing wave. It is the way of things. It is best if we try not to fight it. The best thing for a boat in harbor is to float, to go with the flow. Don't tie it up too tight to the jetty or it will be left dangling in mid air when the tide goes out. Don't anchor it too tightly to the harbor floor or it will be submerged when the tide comes in. Give it some rope.
So too for us: go with the flow—though it takes some getting used to. Sad is not bad. Sad is no more than the tide going out for a while. It will return. Don't fight it. Learn to appreciate it. So too, when you are full of energy and enthusiasm know that it will not always be so. Try and commit to memory what it feels like when you are full of energy and enthusiasm. It will help to remember such times when the tide has gone out and serve as a reminder that the tide will once more return.
This is how Thomas à Kempis, a fifteenth century monk, described it: