He spoke from the heart, and spoke brilliantly.他的演讲发自肺腑, 讲得很精彩。

You could see that those sentiments came from his heart.你可以看出这些情感是来自他心底的。

I don't want to go away without thanking you from the bottom of my heart.离别之际, 我要向你表达由衷的感谢。