In the Mahā-suññata Sutta (MN 122) The Blessed Buddha points out that suffering arises from clinging and attaching to all impermanent things:
“I do not see even a single kind of form from the change and alteration of which there would not arise sorrow, lamentation, pain, grief, and despair in one who lusts for it and takes delight in it!”
The same is true of all transient feeling, perception, mental construction=intention & sorts of consciousness! If we tenaciously cling to any of them, then we suffer, when they decay!
This passage clearly states, that suffering arises from the attachment to form, not because the form is impermanent, but because we are attached to impermanent form.
When we attain full enlightenment, we do not suffer! This happens not because we make any impermanent things now everlasting!
This happens only because we release our clinging to all impermanent things.
Impermanent phenomena continue to be impermanent, whether we ever gain enlightenment or not. As the blessed Buddha also has explained exactly: “Bhikkhus, whether Tathāgatas appear or do not appear, there is always this constantly established element of Dhamma, this fixed law of Dhamma: All that is conditioned and constructed is impermanent. To this a Tathāgata fully awakens and fully understands. So awakened and thus understanding, he announces, points it out, declares, establishes, expounds, and explains it, classifies and clarifies it: All that is conditioned is actually impermanent…
Bhikkhus, whether Tathāgatas appear or do not appear, there is always this precedent condition and absolute of Dhamma, this anchored law of Dhamma: All that is conditioned and constructed is unsatisfactory, & thus suffering!
To this a Tathāgata fully awakens and fully understands. So awakened and thus understanding, he announces, points out, declares, establishes, explains, and clarifies it: All that is conditioned and constructed is indeed Suffering!
Bhikkhus, whether Tathāgatas appear or do not appear, there is always this situation present, a subtle truth of Dhamma, this safe doctrine of Dhamma: All states are without a self! To this fact anyTathāgata fully awakens and fully understands. So awakened and understanding, he announces, points out, declares, establishes, explains, and clarifies it: All states are without self!” – Anguttara Nikāya I 285
By seeing the impermanence, suffering & selflessness thus in all conditioned things in this and any other world, one naturally becomes disenchanted with everything constructed. Disenchantment leads to disillusion and dispassion towards everything. Within a dispassionate mind craving for everything will gradually fade away (virāga). With this insight one lets go of all attachment.
Being dispassionate, one thereby liberates oneself from all this evil misery… Being liberated, one knows that one is liberated, has ended rebirth, has lived the Noble life, has done what should be done, and that there is nothing more to be done! This means that attaining full freedom from all suffering indeed begins with this very perfect and acute awareness of impermanence…!