One of my favorite teachings from Rabbi Richman. The Nazarite took upon himself extra prohibitions. However at the conclusion he was declared sinful and was made to offer a sin offering to the priest in the temple. This indicates, fasting too much or being too fanatical is actually sinful. The purpose of the Nazarite vow was to correct addiction or extreme personality problems by living for a short time in the other extreme with the end goal of returnimg to the straight and narrow middle road.