One of the hardest lessons from Bhagavad Gita is also one of the hardest things to practise:
You can control your effort, but not the outcome.
You can love someone sincerely, but not control how they love you back.
You can do your best at work, but not control how others perceive it.
We spend so much energy trying to control the result that we forget to give our best to the part that actually belongs to us.