tā / zài / xìn / zhōng / pī / lì / xīn / shēng / tǎn / chéng / de / shuō / míng / le / zì / jǐ / de / xiǎng / fǎ

他在信中披沥心声，坦诚地说明了自己的想法。

In his letter, he openly expressed his feelings and honestly explained his thoughts.