言不由衷Heart

This translates roughly as “Words don’t truly reflect my heart”. It could be expressing the fact one may say things different from what's really in their mind due to social etiquette constraints or certain reasons for concealing real feelings; alternatively, this may symbolize a contrast between outer actions and internal feelings - even though what comes out verbally might appear disingenuous or hypocritical sometimes, deep inside, there still hides an authentic core (heart) which remains unchanged.