The Rebbe explains that a ta’anis dibur (speech fast) does not replace a physical fast or its tzedakah substitute, as each serves a distinct purpose. He reminds that every thought, word, and deed must serve Hashem, urging continual growth in both Nigleh and Chassidus learning.
https://www.torahrecordings.com/rebbe/igroskodesh/016/002/5836