There are certain habits which is constructive in kind others being destructive. Habits are formed by repeated actions or mental impressions. 4th house and moon indicate mind, if it is fix Rashi, it will form firm Habits very difficult to change, where as if movable house it will constitute Habits which can be changed. Dual sign indicate Habits which may or may not be changed. Constructive or destructive it depends on if 4th lord is functional benefic or malefic to ascendant. And running dasha lord lagna lord in fix sign with strength indicate good will power to combat any adversity life.