Depth of one’s heart
“You must come and stay with me next time you are in town,” said Ira to her friend. “And I mean it from the depth of my heart.”
When you say something from the depth of your heart you are being very sincere.
This means to regard things or situations impartially.
“Don’t let your emotions overpower you. Look at the problem with a detached mind. I’m sure some solution will be found.”