Doing so may cause an individual to waver in the practice of Stoicism. We are making progress to gain tranquility in our lives. If you are making efforts and progress and improving yourself it is not necessary to tell other people. It is like going to the gym to show off rather than focusing on better health.
A cause of this may be seeking external validation. This means a person gains a sense of self-pride when others approve of their behavior, work, thoughts, etc. He/she needs someone or something to show that they are good at something and are good enough. Often this may be due to a lack of confidence.