In any given material circumstance what can be done or said to soundest effect? Whatever that is, it is in your power to do it or say it - and make no pretence of 'obstacles in the way'. You will never cease moaning until you experience the same pleasure in making an appropriately human response to any circumstance you meet or face as the hedonist does in his indulgence - a response, that is, in keeping with man's constitution. Because you should regard as enjoyment any action you can take in accord with your own nature; and you can do that anywhere.
Now the roller does not have the gift of following its own movement wherever it will, nor does water or fire, or anything else subject to a nature or life without reason: there are many barriers or impediments in their way. But mind and reason have the power, by their nature and at their will, to move through every obstacle.
Keeping clear in your view this easy facility of reason to carry through all things - like fire rising, a stone falling, a roller on a slope - stop looking for anything more. Any remaining hindrances either come from the corpse which is our body, or - without the judgement and consent of our own reason itself - have no power at all to break or harm.
Otherwise, anyone meeting such hindrance would immediately become bad himself. With all other organisms any harm occurring to any of them makes them worse in themselves. But in our case, to put it so, a person actually becomes better and more praiseworthy for the right use of the circumstances he meets. Generally, remember that nothing harms the citizen of nature other than what harms the city: and nothing harms the city other than what harms the law. None of our so-called misfortunes harms the law. So what is not harmful to the law does not harm either city or citizen.
Chapter 33 of Book 10 is one long-winded way of explaining the unique nature of humans, who have the ability to reason, which enables us to turn any perceived obstacle into an opportunity for growth to be better. Life, therefore, is viewed an a cauldron of experience. Humans proceed from one learning experience to the next, until any experience they face is consumed and becomes a part of them - like an unquenchable fire.
I read this really neat science fiction book as a sophomore in high school, called Ender's Game. In a nutshell, the books is about a boy who is recruited by a global military, whose goal is to defend the world from an invasion of aliens akin to insect hoards. The commanders of the military school that Ender is sent to, are tasked with shaping brilliant children into killing machines. Ender's education quickly heats up to the point when the commanders throw anything and everything at him. After establishing rules, the commanders break the rules and force Ender and his squad to act and react to unfair situations. They are trying to prepare him for anything that he will have to face when he battles the alien hoards.
Our lives may not require us to fight alien hoards, but our mindset should be similar - that when any obstacle or event happens to us, we are mentally resilient to meet it head on. Stoicism aims to prepare us for all events and obstacles.