Trines are considered to be highly beneficial aspects, instilling fortune on those individuals who have them in their natal or progressed horoscopes. The notion behind this is that there is a natural and free flow of energy between the two planets.
Astrologers tend to think that the trine gives such a free flow of energy to the person who is fortunate enough to have one that he may stop trying: in such a case, a trine would be considered to pose more of a negative influence than a positive.