Because, a vast majority of it isn’t in your control. But a tiny percent of life actually depends on your choices. And those choices in the course of time can alter your fate.
You may win or lose today. But in the end, there is the drum roll and everything that you did/did not have today will fade away.
So, don’t take it too seriously. Too much to the heart. Just do what best you can.
Robert Frost, the great poet that he is, put life in a simpler perspective,“In three words I can sum up everything I’ve learned about life: it goes on.”