Majority is the point at which the individual attains the capacity for independent survival. This does not mean that they do not still have recourse to their parents for practical or psychological support, but that they could sustain themselves without that support.
Separation and joining at this stage continues to have an aspect of simple exploration, but becomes more directly focused on production. This should not be taken as a simple economic process: it includes learning to participate effectively in social and political activities that manifest our values. Values are the manifestation of our life tone through actions guided by our ethical codes. They are not simply rules of conduct. Rules applied without the guiding touch of love are at best amoral.
Unless they have received deep orientation to the dynamics of romantic relationships from their guardians, most people should not consider forming a permanent romantic alliance until well within their majority. Simply put, relationships succeed because they create success for the community that nurtures the couple. This can be manifested in many contexts: work, church, charity, friendship. Until we have come into some sense of our full power as social participants, we will lack insight necessary to the choice of a life partner.