惊觉相思不露只因入骨
[jīng jué xiāng sī bù lù zhĭ yīn rù gú]
The phrase can be roughly translated as 'Suddenly Realized That Missing You Silently Was Because of Being Deeply In Love.' It implies that a strong and deep emotion, usually love, is hidden but powerful, expressing the intense feeling of missing someone only when one has fallen deeply for them.