Friends:
 

When Experiencing Impermanence one comprehends the futility of clinging!

The Blessed Buddha once said:
What, Ananda, is experiencing impermanence, inconstancy & transience?
When a Bhikkhu, having gone to a forest, to the foot of a tree, or to an empty
place, reflects: all Form is Inconstant, all Feeling is Fleeting, all Experience
is Impermanent, all Mental Construction is Transient, all Consciousness is
Momentary and in this way remains noting the impermanence, inconstancy
and transience of these 5 Clusters of Clinging...
Then this, Ananda, is the experience of impermanence...,
The perception of inconstancy... &
The sensation of transience...

Source (edited extract):
Numerical Discourses of the Buddha. Anguttara Nikāya AN 10:60, AN V 108ff.
Girimananda Sutta http://www.accesstoinsight.org/tipitaka/an/an10/an10.060.than.html

Buddha furthermore explained:
Bhikkhus, there is no lasting materiality, no lasting form whatsoever...
there is no lasting feeling whatsoever... 
there is no lasting perception whatsoever... 
there is no lasting mental construction whatsoever... 
there is no lasting conscious awareness of anything whatsoever...
there is permanent, everlasting, eternal, not subject to change,
not transient, not vanishing, that will last as long as eternity... !!!
SN 22.96/vol. iii, 144 
 

All formations, all constructions are impermanent, transient, vanishing...
MN 35/vol. i, 230
 

Whatever can arise and emerge, that also will surely cease...
MN 56/vol. i, 380
 

Comments from the classical commentaries:

Impermanence is not Evident unless specifically looked for:
False Apparent Continuity covers up and camouflages Impermanence:
The characteristic of impermanence does not become apparent because,
when rise and fall are not given attention, it is concealed by continuity...
However, when continuity is disrupted by observing rise & fall here & now,
the characteristic of impermanence becomes apparent in its true nature.
Vism. Ch. xxi/p. 640

Moments of mental states always change as Iron darts hit:
Observing the abrupt Change of all States discloses their discrete nature:
When continuity is disrupted means, when it is exposed by observation of
the perpetual alteration of states as they go on occurring in succession.
For it is not through the connectedness of states, that the characteristic of
impermanence becomes apparent to one who rightly observes rise and fall,
but rather the characteristic becomes properly evident through their discrete
disconnectedness, regarded as if each moment were iron darts, hitting in on
reality one by one separately, instead of as a continuous flow of slow change.
VismA. 824

All states rise and fall. This characteristic of change, ageing, & evanescence
is the universal impermanence of all worldly. Nothing here escapes change!
It is a distortion of view, perception, and thinking to regard anything as lasting!
Impermanence inherently implies suffering as all what is liked will evaporate!
Impermanence implies no-self as nothing remains identical as same identity!
Whether internal or external: It is only passing states - material & mental - ...
Experiencing impermanence thus also means seeing suffering and no-self!

When realizing that all states passes on and evaporates instantly,
one realizes the impossible futility inherent in all forms of clinging.
It is like sand running out between the fingers. It can never be kept!
Nothing can ever be kept, owned, possessed, maintained, or retained!
So let it go. Release it! Relinquish it all. Do not fear. Nothing lasting is lost!
It was never your's anyway. It will go away by itself anyway. It is pain anyway!
It was never really the same anyway, & it will never ever return again anyway...

More on impermanence, inconstancy, & transience (Anicca)
Anicca (Impermanence) According to Theravada (Bhikkhu Ñanamoli)
http://www.accesstoinsight.org/lib/authors/various/wheel186.html
http://What-Buddha-Said.net/library/DPPN/wtb/a/anicca.htm
http://What-Buddha-Said.net/drops/II/Transient_formations.htm
http://What-Buddha-Said.net/drops/II/Perceiving_Transience.htm
http://What-Buddha-Said.net/drops/III/Impermanence_Anicca.htm
http://What-Buddha-Said.net/drops/II/The_Internal_Transience.htm
http://What-Buddha-Said.net/drops/II/The_External_Transience.htm