Epictetus starts his famous Enchiridion with the observation that somethings are under our control, and some are not. This simple and obvious observation sits at the heart of his system of thought and living. What is in our control Epictetus insists are our judgment, our desire, aversion, and mental faculties in general. Everything else is deemed to be outside our control, even our own bodies.
Epictetus insists on this distinction at the outside because it guards from sorrow. Mistaking things that are out of our control to be in our control will lead to suffering when things don't go as we plan. If we understand what really belongs to us then we will be unhindered in our goals and no one will ever be able to harm us.
Because the rewards are so great we should seek to implement this truth in our lives. Everyday we must ask ourselves if our impressions of things are accurate, and then if what we encounter in our daily living is in or out of our control. If it is out of our control, we should not be concerned with it.
If my goal is to lose weight, I am seeking something outside of my control in an absolute sense. Of course we can undertake actions to cause our bodies to lose weight, but I have noticed very little direct control. You may eat right for a week and lose no weight. You may cheat on your diet and lose 2 pounds. You might be stuck at a plateau for a couple weeks only to lose five pounds quickly.
As in dieting, so in life in general. Although we can take actions that make certain events probable, we cannot directly control external things. I can take every effort to cut a tile correctly and it might snap in half. I can follow every step in a recipe with utmost care, but the food still taste bad. Life doesn't go this way all the time, but if our focus is on things that we cannot control we will be met with disappointment on a daily basis.
The way of freedom and happiness is to instead only focus on what we do control. And so we count ourselves successful if we keep to our dietary plans whether or not we lose the weight. We cut the tile as best we can and count our desire and intention and the action that flows from them as what matters. Breaking a tile is out of our control, but our intentions and desires are in our control.
If we refuse to turn aside from keeping this discipline, if we only focus on what we actually do control, then we will find happiness and freedom. The directness and brevity of this statement should not mislead as to the difficulty of accepting what is in and out of our control and the need to re-orientate ourselves to this truth constantly. To that end I encourage you to forgive yourself and move on quickly whenever you find yourself focused on things not in your control. Don't beat yourself up, just ask of the next thing that presents itself as important to you: Are you in my control? If not, don't worry about it one bit.