In the horoscope we have 12 houses and out of 12 houses 4 are Angular (1,4,7,10) and 3 are trines (1,5,9) houses. The first house is most powerful among all houses because this house is both (Angular & Trine). The first house belongs to self and soul. If our first house is strong means our inner soul has power to fight against all odd situations in our life.
The strength of first house depends upon its lord, planet sitting in first house and aspect of benefic planets.