This really resonated with me, as I am often the victim of my own thinking, making mountains out of mole hills if you will. I assumed what needed to be done would be difficult, or a situation came up that I perceived to be negative caused suffering. My monkey mind went into overdrive and I took the normal shit that happens and turned it into a nightmare. What the hell!
Sure the Buddha was right; life has more than it share of dukkha (pain and suffering), but how much of it is self imposed? As I have been studying stoicism recently I begin to notice certain parallels with Buddhism. Could the assumptions we make about things, that Marcus Aurelius is talking about be yet another cause of dukkha, much like craving, desire, and attachment?
At the moment you start to say this is difficult, or I hate this situation, you are making assumptions and most of these are what will happen in the future. In fact in retrospect you find that most of your assumptions were bullshit.
Maybe the answer is in dealing with things as they occur in the present, without assumptions, expectations, and above all withholding judgment.
A bit of stoicism, Buddhism, and lots of yoga and meditation might help too.