In Vedic Astrology, Lagna is calculated by the position and the aspect of Sun in Earth during our birth time in a particular place. So Sun is having much importance in our life.

Moon sign is where the Moon sits at the time of our birth. As Moon is very close to Earth, effects of Moon in our life is also more important like Sun. Mahadasha and Antardasha periods are calculated based on Moon sign.

Sun and Moon both are very much important in Astrology comparing to all other planets. Sun represents our Soul and Moon represents our Mind. Mind is the key element for success in the materialistic world. So Moon is used to calculate mahadasha. So Moon become more important and Sun become less important regarding Dasha calculations.

Planets are not having self luminescence (except Sun), but stars are having them. So, We should not see only the planet and the house, but we also should see, the stars where the planet sitting.

We are all destined to have a particular kind of life from our past life and have taken birth at a particular time, to a particular parents based on our wishes from the past life.

What is destiny? it is about for what we born in this birth, in this world, whether we born to live like a play boy only to enjoy or we were born to live like a priest like Vivekananda?. This is decided by the supreme thing, we born, live in our own way, die, and then reborn. The destiny decides our Lagna, and the position of Moon.

By the way, if Moon denotes our Mind the most important thing in the materialistic world, then Sun denotes our soul which going to exist even after our death. Thus both become important.

We all born to clear our bad karmas if any, and also to clear good karmas because both are weighing well and they are pulling us back to the materialistic world. Destiny of all soul is to reach the divine, the Supreme Lord. You name it as Mahadev or Narayana or Muruga or any other name you wish, but the divine order for all of us to attain moksha that is our destiny. No astrologer can predict our destiny from our birth chart. Birth chart can say some thing about our current birth. But the native has to find himself about the divine order or the destiny.