From Marcus Aurelius’s Meditations:

“External things are not the problem. It’s your assessment of them. Which you can erase right now.
If the problem is something in your own character, who’s stopping you from setting your mind straight?
And if it’s that you’re not doing something you think you should be, why not just do it?
—But there are insuperable obstacles.
Then it’s not a problem. The cause of your inaction lies outside you.
—But how can I go on living with that undone?
Then depart, with a good conscience, as if you’d done it, embracing the obstacles too.”

“Concentrate on what you have to do. Fix your eyes on it. Remind yourself that your task is to be a good human being; remind yourself what nature demands of people. Then do it, without hesitation, and speak the truth as you see it. But with kindness. With humility. Without hypocrisy.”