Stoicism helped me build the ability to care about the things in my power to change, and not stress about things that aren't. Very useful in any job or personal situation that includes a lot of ambient stress.
"To conclude, always observe how ephemeral and worthless human things are, and what was yesterday a speck of semen tomorrow will be a mummy or ashes. Pass then through this little space of time conformably to nature, and end your journey in content, just as an olive falls off when it is ripe, blessing nature who produced it and thanking the tree on which it grew."
It makes me appreciate everything so much more and I feel like a fool for worrying over little things.
"Your soul takes on the color of your thoughts." P59
"Awaken; return to yourself. Now, no longer asleep, knowing they were only dreams, clear-headed again, treat everything around as a dream." P76
"It's normal to feel pain in your hands and feet, if your using your feet as feet and your hands as hands. And for a human being to feel stress is normal - if he's living a normal human life. And if it's normal, how can it be bad?" P76
"You can hold your breath until you turn blue, but they'll still go on doing it." P102
"Leave other people's mistakes where they lie." P122
If you like randomly leafing through Meditations, I've made a site that would be right up your alley