one's innermost thoughts; all that is in one's heart
Refers to the full depth or extent of one's feelings, thoughts, or emotions. Often used when expressing everything one feels, especially in emotional contexts. Similar to 思いの丈 (おもいのたけ).
See also: 思いの丈 (おもいのたけ)
I poured out my heart to her.
I wrote down all my innermost thoughts in the letter.