What we can control, we need to.
What we cannot, we need to let go.
Many things fall within our control, like our opinions, desires, and aversions. Controllable things are those we initiate and carry out. Many more things we have no direct control over, like others’ thoughts and actions, situations in which we find ourselves, or events we learn of.
Things we can control arise from our mind while those we cannot arise from others’ minds.
Theoretically, this should make life very straightforward. Why put time and energy into trying to manage that which is beyond my purview? The only hope I have to accomplish this is through being such an excellent example that I move others. How? By working with that which I can govern: my thoughts. My thoughts, unperceived by others, give rise to my actions, which are perceived by others. So by controlling that which arises from within me, I better myself and possibly help others.
But it all begins with controlling what I can and letting go what I cannot.