Unrepeatable

You never return to the same place.

It is a different place already.

You can never return. To return means to go back to the same place. But it never stays the same. It has already changed forever.

Each moment spent in a place cannot be repeated.

Just like these words - if you were to return to them after an absence - they will be different - even if slightly, which means not the same, almost the same, somehow different, not exact, similar- or bearing a resemblance to- or reminding you of these same words you read that other time - before.