Thanks for mention. Medium, broken as it is nowadays, didn't notify me so my response is delayed.

Perhaps I have already thrown the following short poem your way, I honestly can't recall, but anyway.

Well, it should be understood
There's no evil, there's no good.
Love the Devil as your brother,
God will love you like no other.

In other words (and yes, this reflects even in the realm of concepts), pleasure and pain are both a sensation, a feeling. And a passing one to boot, as you correctly observe. Change is immutable while it lasts and everything is recorded as effects that become causes in the very fabric of the world, that is to say the change itself. But change has a traceable start.

Yet from another angle – since I am not born, I also cannot die. I don't live, but I am not dead either. I, simply, am. For now, as you aptly put it, “Unchanging I change.”