Man's joy is to do man's proper work. And work proper to man is benevolence to his own kind, disdain for the stirrings of the senses, diagnosis of the impressions he can trust, contemplation of universal nature and all things thereby entailed.
Three relations. First, to your environment; second, to the divine cause which is the source of all that happens to all men; third, to your fellows and contemporaries.
In this first passage, Marcus outlines all three disciplines of Stoicism. First, the discipline of action - which is to do "proper work". Proper work is to be kind to others and to exercise the discipline of assent and desire. And what are the disciplines of assent and desire? He explains the discipline of assent is to disdain (or have contempt for) the stirrings (or impulses) of the senses; and to identify and understand impressions. Lastly, he explains the discipline of desire as accepting the universal nature of things. Ultimately, things in the universal domain are out of our control and therefore we have to accept them for what they are.
In the second passage, he talks about our relationship with our environment; our relationship to change and our relationship to our fellow men. With regard to the environment, we always need to delineate between things in our control and things out of our control. And then to the divine - we have to accept and love what the Gods or Universe mandate; else we will be frustrated. And lastly, we have to work with others; help where we can and not blame those who are not enlightened.
(see also Citadel p. 173, 240)