The human rebirth is said to be extremely rare. The Majjhima Nikaya (129 Balapandita Sutta) compares it to a wooden cattle-yoke floating on the waves of the sea, tossed this way and that by the winds and currents. The likelihood of a blind turtle, rising from the depths of the ocean to the surface once in a hundred years, putting its head through the hole in the yoke is considered greater than that of a being in the animal realm, hungry ghost realm or hell realm achieving rebirth as a human. This is because, according to the sutta, in these realms there is no Dhamma (Sanskrit Dharma), no practicing what is right, no doing what is wholesome, and no performing of merit. However it is generally implied that if one is already living as a human they will continue to be reborn in the human world based on good works and so they will be one again and again as long as they are moral and good in the ways described in Buddhist rules regardless of whether or not they are Buddhist themselves. The idea is that one must be good and moral because falling below the human realm is dangerous as the odds of one becoming a human again with any great frequency is slim.
Is the implication correct? That a human being will continue to be reborn in the human world based on good work? I've heard both sides...this one and also that human rebirth is rare in all circumstances....even if one conducts himself well.
I have this sense of angst about my next life sometimes and wish deeply to be able to continue the practice of the Dharma...that's why, the idea of it almost being impossible to be reborn as a human is very discouraging.