To understand the "Art" of Impermanence is not difficult actually... we are 'exposed' to it everyday:
we hear news of sudden death such as road accidents, of so and so is hospitalised for terminal illness, of how a family's happiness is destroyed by tragedies such as in natural disasters, etc.
The problem is, even though clear signs of 'Impermanence' is right in front of our face, we still think we are 'safe' and that these 'incidents' will not happen to us...
Naively we think that 'our time is still long' and so no need to take any drastic move. Even when we are doing the so-called Dharma 'works', we set conditions and will only willing to do if it is within our comfort zones.
The truth is ... what we think we have seen and 'realised'; like when we witness the death of friend/family or when we ourselves experienced near-death situations, it is still, unfortunately, only on a superficial level... we have never really 'see' it, for if we did, we would have throw everything behind and practice without the need of being told, instructed, ordered, coerced by our compassionate Guru/ Spiritual Guide.
Someone I knew is a cancer survivor, she once told me how painful it was to endure the effect of chemo therapy and that she will never want to go through it again... sadly though, this person never make enough effort to change for better... she is still the same selfish person who is anger-some, nasty, rude, and never offer helps unless there is something for her... when given advice or feedback, she will retort angrily and became very defensive...
Another person survived a horrible car accident, he was seriously injured and was in coma; doctors didn't give him much hope but miraculously he woke up and was healed. Initially he was 'thankful' but then again, once worldly 'wealth' and 'enjoyments' seems more attractive, he just forgotten about the need to help others...