The Buddha identified three kinds of suffering: the dukkha of physical and emotional pain…
The first kind of SUFFERING is the obvious suffering caused by physical discomfort, from the minor pain of stubbing a toe, hunger, and lack of sleep, to the agony of chronic disease. It is also the emotional suffering that arises when you become frustrated that things don’t go your way, or upset about life’s injustices, or worried about money or meeting others’ expectations.
[The second kind] is the suffering caused by the fact that life is constantly changing. Doesn’t it often seem as though the moment you have found happiness in life, it disappears almost at once? … In truth, no moment is reliable because the next moment is always coming along fast on its heels. It is like a constant bombardment of change undermining every state of happiness. The mind never finds a place to sit back and enjoy life without fear…
Furthermore, every day, even during the pleasant moments, do you not experience an underlying unease about the future? This worry and anxiety is a manifestation of the third type of suffering the Buddha identified—life’s inherent unsatisfactoriness due to its intrinsic instability.
Impermanence is not the cause of suffering
We may discover, as the Buddha tells us, that the lack of substantiality or permanence in all that surrounds us gives rise to unhappiness and pain. This does not mean, however, that the experience of impermanence or non-substantiality is itself suffering or the direct cause of suffering. We misconstrue the Buddha’s message if we think it is the fact that all things are impermanent or non-substantial or without a solid self that generates suffering. These basic facts are not the truth of the origin of suffering.
Dukkha is produced not by things themselves or by their insubstantial nature. Rather, our mind has been conditioned by ignorance into thinking that eternal happiness can be obtained through things that are ephemeral and transient.
There is something behind our suffering
Whenever there is pain of any kind—the pain of aggression, grieving, loss, irritation, resentment, jealousy, indigestion, physical pain—if you really look into that, you can find out for yourself that behind the pain there is always something we are attached to. There is always something we’re holding on to. You can read about it: the first thing the Buddha ever taught was the truth that suffering comes from attachment.