'It is my bad luck that this has happened to me.' No, you should rather say: 'It is my good luck that, although this has happened to me, I can bear it without pain, neither crushed by the present nor fearful of the future.' Because such a thing could have happened to any man, but not every man could have borne it without pain. So why see more misfortune in the event than good fortune in your ability to bear it? Or in general would you call anything a misfortune for a man which is not a deviation from man's nature? Or anything a deviation from man's nature which is not contrary to the purpose of his nature? Well, then. You have learnt what that purpose is. Can there be anything, then, in this happening which prevents you being just, high-minded, self-controlled, intelligent, judicious, truthful, honourable and free - or any other of those attributes whose combination is the fulfilment of man's proper nature? So in all future events which might induce sadness remember to call on this principle: 'this is no misfortune, but to bear it true to yourself is good fortune.'
One of my absolute favorite passages of Meditations. I have a pinned tweet with this quote (link).
Life is opinion. If you want to be resilient and tough-minded, this passage is the key to getting there.
Ryan Holiday's book The Obstacle is the Way is based on this idea that we should not view events as unfortunate, but that we should view ourselves as being able to live up to the challenge.
I also love that Marcus calls out the true nature of humans - to be virtuous and more specifically, just, disciplined & temperate and wise & intelligent (the 4th cardinal virtue he doesn't necessarily list, but it is courage).
(see also Citadel p. 36, 68, 122)