孤久则惯情久终腻
[gū jiŭ zé guàn qíng jiŭ zhōng nì]
Gu Jiu Ze Guan Qing Jiu Zhong Ni literally translates to 'loneliness over long turns into habit; deep emotions after time can become tedious,' implying that prolonged loneliness can be normalized, but deep emotions might also eventually lose freshness over time.