Sorrow, lamentation, pain, distress and despair are stressful.
Appiyehi sampayogo dukkho piyehi vippayogo dukkho yamp'iccham na labhati tampi dukkham.
Assocation with things disliked is stressful, separation from things liked is stressful, not getting what one wants is stressful.
Sankhittena pancupadakkhandha dukkha.
In short, the five clinging-aggregates are stressful.
Have you ever wondered why the Buddha felt the need to state and elaborate on the First Noble Truth?
I mean, isn't it obvious that life is stressful?
Who among us does not experience the steady undercurrent of discomfort, unease, dissatisfaction, anguish and suffering?
So why would the Buddha feel compelled to state the obvious?
It seems to me a bit like an emergency room physician telling someone with an enormous head wound, "You have an enormous wound in your head." Uh, yeah. Thanks, doc, I didn't know that.
Do you share my curiosity about this? Maybe I'm missing something obvious (wouldn't be the first time), but I'm genuinely puzzled.
After thinking about this for a bit, here's my hunch about the Buddha's motivation: We humans have developed considerable skill at masking the dukkha that streams through our life.
Specifically, we've created countless ways to defend and deny the reality of our own suffering. Further, we resist those who would point out our problems. Really, we'd prefer not to know.
So, in stating the the First Noble Truth, the Buddha was issuing a wake-up call to the reality of life.
Because as long as we deny reality, our own enormous wound will never heal.