Gradually we become tired of the old, of what we safely possess, and we stretch out our hands again. Even the most beautiful scenery is no longer assured of our love after we have lived in it for three months, and some more distant coast attracts our avarice: possessions are generally diminished by possession.
 
[Wir werden des Alten, sicher Besessenen allmählich überdrüssig und strecken die Hände wieder aus; selbst die schönste Landschaft, in der wir drei Monate leben, ist unserer Liebe nicht mehr gewiss, und irgend eine fernere Küste reizt unsere Habsucht an: der Besitz wird durch das Besitzen zumeist geringer.]

Friedrich Nietzsche (1844-1900) German philosopher and poet

The Gay Science [Die fröhliche Wissenschaft], Book 1, § 14 (1882) [tr. Kaufmann (1974)]
    (Source)

Also known as La Gaya Scienza, The Joyful Wisdom, or The Joyous Science.

(Source (German)). Alternate translations:

We gradually become satiated with the old, the securely possessed, and again stretch out our hands; even the finest landscape in which we live for three months is no longer certain of our love, and any kind of more distant coast excites our covetousness: the possession for the most part becomes smaller through possessing.
[tr. Common (1911)]

We slowly grow tired of the old, of what we safely possess, and we stretch our our hands again; even the most beautiful landscape is no longer sure of our love after we have lived in it for three months, and some more distant coast excites our greed: possession usually diminishes the possession.
[tr. Nauckhoff (2001)]

We gradually grow weary of the old, familiar things we securely hold, and again stretch forth our hands; even the most beautiful landscape lived in for three months is no longer assured of our love, and some more distant shore excites our avarice: what is had loses much in the having.
[tr. Hill (2018)]