It sounds pessimistic to me, as if life is nothing but suffering. Gautama Buddha said that life is suffering, but even he found things to laugh at including himself, I expect. I like one that is purported to have come from him better. "Accept life as it is, not as you would like it to be." This does not mean to can't go ahead and change it whereever you can. But how we accpt it NOW indicates our maturity or lack of it.
I can't really say I like that quote. I'm mature (chronologically anyway, but I think "in general" as well). I don't like the bit about "stoic".
I'm going to make up my own saying: "Maturity is being sure enough of yourself not to hide, or stop being, the 'you' you've always been just because you think you're worrying about doing/thinking something that appears to be, or that might make you look, immature." (I'm no more stoic now about some realities than I've ever been, and I don't plan to ever be.)