你的左胸膛一定很拥挤
[nĭ de zuŏ xiōng táng yī dìng hĕn yōng jĭ]
'Your left chest must be very crowded' implies the owner believes the loved one keeps a variety of emotions/affairs (such as love, memory, or concern) hidden in their hearts. Here left chest refers to close to heart since heart is on the left side in anatomy structure.