01
The idea
The Stoic position is not that health, money, love and reputation are worthless. It is that they are indifferent — not components of a good life — while still being reasonably preferred. You may pursue them, hard. You may not count them as what makes your life good.
The reason for this severity is structural. If anything outside your character contributes to a good life, then fortune can partly destroy a good life, and the entire promise of the school collapses. Locating the good exclusively in virtue is what buys invulnerability, and nothing cheaper will buy it.
The price is a description of loss that many careful readers find unlivable. If your child is an indifferent, something has gone wrong with the account. The Stoics accepted this consequence more readily than most of their successors have, and the honest thing is to put the difficulty in front of you rather than smooth it.
02
Why this matters
Where you locate the good determines what can destroy you. Locate it in results and every downturn is an existential event. Locate it in character and the downturn is expensive without being fatal.
It also settles the question of what to do when doing right costs you something. If externals were part of the good, the calculation would be genuinely open. On the Stoic account it is not — which is precisely why the philosophy produces people who resign, refuse, and speak up.
And it disciplines ambition. You are free to want the outcome as hard as you like, so long as you never let it become the thing that makes you acceptable to yourself.