It is defined by what your expectations and aspirations in life are. What are the things that make you feel you have arrived in life and have what it takes to be happy? So its a RELATIVE concept. But still there are some common denominators that we can count as essential to SUCCESS in the modern competitive world.
There have to be certain materialistic trappings like a residence, vehicle, a good spouse, child/children, an appreciative boss or peer group at work, a job that pays well and uses your talents, supportive family, a happening social circle, time to pursue hobbies etc etc etc..its an aspirational list and has no beginning and no end:)
Astrologically, can one find if a person will find success late or early in life? We have certain sportpersons and actors/singers who at a very early age started achieving accolades and knew their destiny path in this lifetime. Some achieve a comfortable level in life in their mid 20s while there are others to whom success is denied till after 30s.
On careful study of a person's Horoscope, ONE CAN DEFINITELY PREDICT AND GIVE TRENDS WHEN A PERSON WILL ACHIEVE SUCCESS IN LIFE?
The PLANET responsible for this greatest achievement in Life is SUN-THE FUEL, THE SOUL, THE VITAL POWER of any Organism, especially the HUMAN BEING.
*The MORE EXALTED/FRIENDLY SIGN/YUVAVASTHA the Sun is in the higher the chances of early success.
*The Closer the Sun is to its Debilitation Point, the more delayed the success.
* DIGBALA is of extreme importance. Sun when placed in 10th hs gives maximum DIGBALA and in 4th the lowest.
* If SUN is eclipsed by Rahu/Ketu or falls in the Rahu-Ketu axis, the brilliance of a person is reduced and his talents will not shine through.
*An uncanny observation is that LORD OF DELAY-SATURN will be strong WHEN SUN IS WEAK IN YOUR HOROSCOPE.
* A STRONG SUN WILL LEAD TO Father/Father Figure being the PUSH IN THE PERSON'S LIFE. He will give that authority push early in life so that they practice/rehearse their talents, grab any opportunuty and give a clear direction in Life.
*A STRONG SUN+STRONG MARS = 99% EARLY SUCCESS IN LIFE.
There are ofcourse many combinations that work towards for Success but A COMMON FACTOR WITH ALL SUCCESSFUL PEOPLE IS THE SUN BECOMING STRONG AT THE JUNCTURE WHEN THEY ATTAIN SUCCESS.