They made me laugh with testosterone)
Temperament is a set of innate properties of the nervous system that determine the strength, speed, plasticity of nervous processes. It is impossible to change temperament, but you can develop compensating character traits in yourself. In people who work on themselves, with age, the sharp lines of temperament smoothed out. There is even such a thing as a "well-mannered choleric" - a person who has learned to control his emotional outbursts. Similarly, there can be a "well-bred melancholic" - a person who has developed in himself those qualities that he lacked for a full life in society.
Sanguine / choleremic / melancholic is an outdated classification that is no longer used in science. And in your question, I suspect that it is not about melancholic temperament, but about self-doubt and "non-masculine" behavior. Here we need to work with a psychologist, testosterone clearly has nothing to do with it.
This classification of types of temperament with sanguine and choleric people has come down to us from very ancient times and is currently not quite relevant. Melancholic in it is usually defined as "shy, prone to constant experiences, acutely reactive to external factors" and so on. That is, there is a description of a typical neurotic with the corresponding external manifestations - self-doubt, anxiety, irritability. These are not congenital traits of temperament, but acquired psychological problems. In most cases, a conversation with a psychologist or a course of psychotherapy helps a person to cope with such problems and, as a result, to stop being "melancholic".