The things that are under our control are by Nature free, unhindered, and unimpeded. But the things that are not under our control are by Nature feeble, slavish, hindered, and belonging to another.
We may give thanks to Nature in knowing that she has not been unkind to us, not cruelly having bestowed upon us anything that can be taken away.
What I have translated as "the things that are under our control" is perhaps more literally and accurately translated from the Greek as "the things which belong to us". There are many things that we mistake to be our own belongings, and we are consequently grieved and feel cheated when they are taken from us. Our social status, job, reputation, possessions and wealth, even our friends and loved ones, fit into this category. Yet they never belonged to us in the first place, subject, as they were, to factors outside of ourselves. Economic forces, treachery, disease and a multitude of other factors outside of our control can take them away from us.
The things that do belong to us, by contrast, are those things over which external circumstances have no power; that is, the things over which we exercise absolute autonomy and authority. What truly belongs to us is our response to what does not belong to us. If we value liberty, if we wish to be always "free, unhindered, and unimpeded", then we must focus on that which is naturally free, unhindered, and unimpeded. Fortunately, these are the very things which are already by Nature our own property.