Why do we have to think about impermanence?

What we mean by impermanence is that things keep on changing. 

These changes are not something that can be stopped, they are not things we want to change, are not things that we put effort into changing. These changes naturally occur.

When we contemplate impermanence, we start to realize that this change means that moment by moment there are also opportunities, there are
limitless opportunities, continuously.

To really understand this, this is the purpose of contemplating impermanence.

HH, 17^th Karmapa

Ogyen Trinley Dorje

From Kamashila
Short-Ngon-dro teaching
Germany, 2014